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TST3-CT-2003-506075

SEES

Sustainable Electrical & Electronic System for the Automotive Sector

Specific Targeted Research or Innovation Project(STREP)

Priority 6.2: Sustainable surface transport

D4: Analysis and Demonstration Activity for E&E Recycling

Due date of deliverable: 30 June 2006Actual submission date: 30 June2006

Start date of project: 1 February 2004 Duration: 36 months

WP 4 leader: Kate Geraghty, Martin Goosey (RHEMEL) (until April 2006)Mercedes Malaina (IRSA) (from May 2006)

WP 4 partners: Julio Rodrigo (URV)Miren Larrañaga (GAIKER)

Data file: D4_Report.doc Revision: Final (30.06.2006)

Project co-funded by the European Commission within the Sixth Framework Programme (2002-2006)Dissemination Level

PU Public XPP Restricted to other programme participants (including the Commission Services)RE Restricted to a group specified by the consortium (including the Commission Services)CO Confidential, only for members of the consortium (including the Commission Services)

RHEMEL, IRSA, URV, GAIKER D4: Analysis and Demonstration Activity for E&E Recycling

Table of Contents

1 Introduction.............................................................................................................6

1.1 Summary of D4 Report...............................................................................6

1.2 Study on EES, Data Acquisition and Database Creation............................7

1.3 Mechanical Recycling.................................................................................8

1.4 Chemical Recycling.....................................................................................8

2 Study on EES, Data Acquisition and Database Creation.......................................9

2.1 The different types of EES collected...........................................................9

2.1.1 Definition of recycling groups........................................................9

2.1.2 Study of physical samples of EES components..........................11

2.2 Developed data format..............................................................................12

2.2.1 File template for EES..................................................................13

2.2.2 Sample files in database.............................................................15

2.3 Conclusions...............................................................................................16

2.4 Identification of Components for Chemical and Mechanical Recycling Studies......................................................................................................17

3 Mechanical Recycling...........................................................................................19

3.1 Identification of Available Technologies for Mechanical Treatment..........19

3.1.1 Overview of mechanical recycling technologies.........................19

3.1.2 Size Reduction............................................................................20

3.1.3 Separation Methods....................................................................21

3.2 Testing and Demonstration of the Technologies for Mechanical Treatment25

3.2.1 Mechanical Processes for Recycling EES Components.............26

3.2.2 Mechanical test for junction boxes..............................................26

3.2.3 Mechanical test for wire harnesses.............................................33

3.2.4 Mechanical test for EES mixed fraction......................................37

3.2.5 Mechanical test for motors and alternators.................................44

3.2.6 Battery Recycling........................................................................46

3.2.7 HID Lamps Recycling..................................................................46

3.2.8 Liquid Crystal Display (LCD) Recycling......................................47

3.3 Copper metallurgy.....................................................................................49

3.4 Conclusions...............................................................................................52

4 Chemical Recycling..............................................................................................52

4.1 Identification of Technologies for Chemical Recycling..............................52

4.1.1 Recycling of Electronic Assemblies using Chemical Recovery methods......................................................................................53

4.1.2 The Material Characterisation of Printed Circuit Boards.............57

4.1.3 General Electronic Scrap Recycling Considerations..................58

SEES – Sustainable Electrical & Electronic System for the Automotive of 247


4.1.4 Details of Chemical Recycling Technologies..............................58

4.1.5 Overview of Key Chemical Recovery Methods...........................59

4.1.6 Summary and Conclusions for Chemical Recovery Methods.....70

4.2 Chemical Recycling Study on selected Components...............................71

4.2.1 Comminution of PCB samples for chemical recycling................71

4.2.2 Results and discussion...............................................................75

4.2.3 Populated PCB characterisation study.......................................75

4.2.4 The lambda Sensor Study...........................................................82

4.3 Proposed Electrochemical metal Recovery Route....................................84

4.4 Chemical Recycling Technology...............................................................85

4.4.1 Process Overview and Previous Work........................................85

4.4.2 Process Control.........................................................................112

4.4.3 Costs.........................................................................................123

4.5 Demonstration of the leaching-electrowinning reactor at Imperial College, London....................................................................................................124

4.6 Conclusions.............................................................................................124

5 Application of SEES Evaluation Methodologies to six EES Products................125

5.1 Introduction.............................................................................................125

5.2 Summary of the two Developed Methodologies.....................................125

5.2.1 Recyclability and Recoverability Potential of EES (Methodology 1)...............................................................................................126

5.2.2 End-of-life Scenarios of EES (Methodology 2).........................129

5.3 Main Results and Conclusions of the 6 Case Studies............................130

5.3.1 Passive Junction Box (PJB) Passenger Compartment -..........131

5.3.2 Seat Mechatronic......................................................................140

5.3.3 Passenger Smart Junction Box (PSJB)....................................154

5.3.4 Wire Harness Engine Compartment........................................169

5.3.5 Alternator...................................................................................172

5.3.6 Lambda Sensor (exhaust gas)..................................................186

5.4 General Comments and Conclusions.....................................................189

6 Conclusions........................................................................................................190

7 References.........................................................................................................194

8 Appendix.............................................................................................................200

8.1 Appendix 1: Conditioning of PCBs for Chemical Recycling....................200

8.1.1 PCB1. Lead-free samples (Smart & Passive JBs)....................200

8.1.2 PCB2. Electronic Modules (Lead-free).....................................201

8.1.3 PCB3. Smart JB passenger......................................................202

8.1.4 PCB4. Electronic modules (tin-lead).........................................203



8.1.5 PCB 5. Passive Junction Boxes................................................204

8.2 Appendix 2: Chemical Analysis Data......................................................205

8.3 Appendix 3: EES components database................................................211

8.3.1 Lambda control exhaust gas sensor from EoL vehicle.............211

8.3.2 Wire harness from EoL vehicle.................................................213

8.3.3 Wire Harness (passenger compartment, OPEL – Vectra)........215

8.3.4 Passive junction box engine compartment from EoL vehicle....217

8.3.5 Relay from EoL vehicle.............................................................218

8.3.6 Small fuse from EoL vehicle......................................................220

8.3.7 Small fuse from EoL vehicle......................................................222

8.3.8 Passive PCB junction box (passenger compartment)...............224

8.3.9 Smart Junction box (engine compartment, OPEL – Vectra).....226

8.3.10 Smart junction box (passenger compartment, OPEL – Vectra) 228

8.3.11 Seat mechatronic (passenger compartment, FIAT)..................230

8.3.12 Electronic Control Unit (passenger compartment, MATRA).....232

8.3.13 Alternator from EoL vehicle.......................................................234

8.3.14 Starter motor from EoL vehicle.................................................236

8.3.15 Cassette player / radio from EoL vehicle..................................238



1 Introduction

1.1 Summary of D4 Report

This report presents work undertaken by Rohm and Haas Electronic Materials Europe Lim-ited, its subcontractor Imperial College, London, Indumetal Metal Recycling, Fundación Gaiker and Simpple at Universitat Rovira i Virgili over a period of twenty-two months as part of Work Package 4 of the EU funded, Sustainable Electrical and Electronic Systems for the Automotive Sector (SEES) project. Work Package 4 entitled “E&E Recycling” is divided into three major tasks. The combined and over-arching objectives of these combined tasks that comprise Work Package 4 is to analyse and evaluate the technical, economic and environ-mental feasibility of various chemical and mechanical recycling technologies for selected EES components and materials in order to recover the most valuable materials (gold, silver, platinum, copper) and to obtain a recyclable plastic fraction.

The first of the three tasks comprising Work Package 4 is Task 4.1 – Study on EES, Data Ac-quisition and Database Creation the results of which, were presented in the milestone report M2 Elaboration of E&E Systems. The results of this task deliver a database containing im-portant technical and recycling information on the different electrical and electronic systems on the market. Details such as the weight, dimensions, composition, etc. of the studied EES in the recycling studies are presented. As well as information on the different aspects of EES components present in cars. The database also supports the definition of recycling pro-cesses (WP 4 and WP 5), the improvement of designs to advance dismantling and recycling (WP 8 and WP 9), and the acquisition of data for assessing different scenarios (WP 7 and 11).

The remaining two tasks in Work Package 4 are Task 4.2 Chemical Recycling and Task 4.3 Mechanical Recycling. Whilst both these studies are aimed at analysing and evaluating dif-ferent recycling approaches to recover valuable metals and plastic fractions from selected EES, both studies were structured similarly and were carried out concurrently requiring the partners involved to work in close collaboration. Rohm and Haas Electronic Materials (RHEMEL) in collaboration with its subcontractor, Imperial College, London has undertaken the research into chemical recycling technologies for automotive EES whilst, Indumetal Re-cycling SA (IRSA) was responsible for undertaking the mechanical recycling aspects of the study. Both of these lead industrial partners have received technical support from both GAIKER and Simpple based at the Universitat Rovira i Virgili throughout the duration of tasks 4.2 and 4.3.

The first stage of both tasks necessitated scoping studies to be undertaken in order to identify all the available chemical and mechanical recycling techniques for treating various EES components that were identified and prioritised in the D1 Report “Integrated Assess-ment of Automotive EES”. A detailed description of all the new, emerging and state-of-the-art chemical and mechanical recycling techniques is presented in this report. As well as a theor-etical discussion of recycling routes for components that were considered unsuitable to go forward to the practical, chemical and mechanical recycling trails is presented.

The specific mechanical and chemical recycling methodologies that has been identified and highlighted have been evaluated during the second phase of tasks 4.2 and 4.3 during the laboratory and pilot scale trials with the findings presented in the this report too. Topics ad-



dressed in this interim milestone report included: the influence of mechanical shredding pro-cesses on subsequent chemical extraction efficiencies for selected EES components; the use of chemical methods to characterise the metal content of printed circuit board (PCB) con-taining devices, size reduction and separation techniques for sorting metals and plastics components derived from the car dismantling process. Additionally, environmental and eco-nomic data has been collated by both RHEMEL and IRSA to support the LCA and LCC eval-uations in the WP7 “Economical & Environmental Studies” of SEES project. This data collec-tion has enabled the determination of the most eco-efficient mechanical and chemical recyc-ling options for recovering valuable metal and plastic fractions from EES components.

The third phase of the tasks 4.2 and 4.3 involved the development and demonstration of the selected chemical and mechanical and recycling processes, the results of which are de-scribed in this report. The findings presented included: the design and characterisation of the leach and electrowinning reactors for the chemical recovery of precious metals from PCB containing devices, developed by RHEMEL’s subcontractor, Imperial College, London; the development of sensors to control the chemical recycling process; the optimisation of the mechanical recycling process, and evaluation of the metal and plastic fractions obtained from the mechanical assessment, both in terms of composition, their potential value added end-use applications and market acceptance. In respect of the chemical recycling study the chemical recycling process was demonstrated by Imperial College London at a demonstra-tion event held in London in April 2006.

This report, D4 presents the edited findings of all the above reports with the inclusion of re-cent improvements in the chemical and mechanical recycling process as well as an overview of the chemical recycling demonstration event hosted by Imperial College during April 2006.

Below is a more detailed overview of the objectives of different tasks.

1.2 Study on EES, Data Acquisition and Database Creation.

The main objectives of “Study on EES, Data Acquisition and Database Creation” are as fol-lows:

A study of the different selected EES components that are derived from first level dismantling of parts and components from end-of-life vehicles (ELV)

The identification and measurement of materials to calculate the potentially recov-erable fractions of selected EES components via manual, second-level dismant-ling

A study of the contaminants and contamination of EES components that could re-duce the quality of the recoverable fractions or that affect recycling processes or which may have environmental impacts.

In order to achieve these objectives a register has been created for each EES component. Every component register contains technical and recycling data sections. Details such as weight, dimensions, composition, etc. of the studied EES have been included in the recycling data section as well as original, technical information from the component manufacturers is presented in the technical section. The database that has been created is a compilation of all the individual registers for each EES component. The database supports the definition of recycling processes, improvements in design for enhanced dismantling and recycling, the ac-



quisition of data for assessing different recycling scenarios and offers a reference for other EES components with similar characteristics.

1.3 Mechanical Recycling

The main activities of Mechanical Recycling include:

A study of different alternatives for the mechanical treatment of different EES components

Investigating and optimising specific mechanical recycling processes (e.g. separa-tion of the metallic fraction, without limiting the plastic fraction recycling)

Proposing an ideal recycling processes that improves the present scenario and verification activities to support these proposals

Input requirements from steel and secondary aluminium producers, from copper smelter, etc…

Characterization and chemical analysis of the different fractions to evaluate the market acceptance for them.

Inputs for LCA and LCC case studies.

1.4 Chemical Recycling

The key objectives of task 4.2 Chemical Recycling include the following:

Conduct lab-scale trials in order to recover valuable fractions from the selected EES components using a variety of chemical processes identified in the D1 Re-port “Integrated Assessment of Automotive EES”.

The evaluation and quantification of the fractions recovered from the different EES components

Obtain a polymeric glass fibre fraction from the EES and determine suitable end-use applications

Investigate the possibility of reusing some of the valuable components on the PCBs

Identify contaminants that reduce the quality (i.e. price) of the recovered fractions or affect recycling processes and environmental & health aspects

Evaluate the different chemical recycling methodologies in order to determine the most efficient and environmentally friendly, based on LCA and LCC studies.

The sequence of identifying all available chemical recycling processes and conducting the laboratory-scale trials have been conducted at RHEMEL’s Coventry facility, whilst the verific-ation of the chemical recycling process has been conducted by RHEMEL’s sub-contractor Imperial College, London.

All research, lab-scale testing and the validation of the selected laboratory tests for the EES mechanical recycling processes has been conducted at IRSA facilities using existing and modified recycling equipment. All the new, emerging and state-of art chemical and mechan-ical recycling methodologies for treating EES components have been identified as well as



theoretical discussion of recycling routes for components that were considered unsuitable to go forward to the practical, lab-scale trials.

Laboratory and pilot scale trials have been conducted to evaluate the combined mechanical and chemical recycling processes for the recovery of valuable materials from end-of-life auto-motive electronic devices, chemical extraction techniques for characterising the metal con-tent of PCB containing devices has also been undertaken. The selected EES have been subjected to state of the art separation processes in order to obtain valuable fractions, the various material streams have been defined according to particle size.

The mechanical recycling processes to optimise the recovery of metals and plastics from mechanical comminution processes have been investigated; a scheme combining some sep-aration operations like vibrating separation, pneumatic classification, magnetic separation, eddy current separation, electrostatic separation, etc., has been defined and chemical recyc-ling approaches have been demonstrated and optimised, and the material composition and market acceptance of the recovered fractions have been analysed.

2 Study on EES, Data Acquisition and Database Creation

2.1 The different types of EES collected

2.1.1 Definition of recycling groupsThe activities in “E&E System Recycling” are dependent of the specific components selected using the matrix created at public document of SEES D1 “Integrated Assessment of EES in Cars”. From a recycler’s point of view different recycling groups have been defined to com-bine components that can be recycled in similar circuits. Table 1 summarises the recycling groups of EES defined at the “EES system recycling” and the selected ESS components at “Integrated Assessment of EES in Cars” after working with a selection matrix with the follow-ing three-step selection process:

Filter 1: Determination of relevant and representative groups of components

Filter 2: Identification of most relevant components from selected groups

Filter 3: Component feasibility for SEES project that depends on considerations of partners from “Assembly Study” and “Shredding Study”.

Table 1. EES components to recycle

SEES component groups Selected component Recycling group

1. Sensors Lambda control exhaust gas sensorMixture of others devices2. Actuators (basic) Pyrotechnical initiators (airbag inflat-

ors and seat belt tensioners)

3. Wire harness / Cables Wire harness (engine compartment) Cables

8. Motors / Generators Starter motor

AlternatorElectric motors and al-ternatos



4. Connection / Protection devices

Passive PCB junction box (engine compartment)

Passive PCB junction box (passen-ger compartment)

Printed circuit boards containing devices

5. Electronic control units (ECU)

Smart junction box ( engine com-partment)

6. Integrated mechatronic components (IMC)

Seat mechatronics

Light mechatronic

12. Entertainment CD player / cassette radio

Trunk multiple CD changer

13. Communication / Naviga-tion GPS navigation system

10. Heating units Rear-window heating ---

SEES component groups Selected component Recycling group

11.Displays / Screens LCD screens

Head-up display (HUD)---

14. Other devices Park pilot (rear bumper ultrasonic sensors) ---

7. Batteries Lead-acid starter battery Batteries

9. Lights / Lamps HID head lights Lamps

As already mentioned in the previous section, one of the main objectives of the “Study on EES and Database Creation” is to create a database of the different EES of cars. The range of EES that can be found in the market and in the dismantling and shredding facilities is very wide but the following criterions have been considered:

Selection of cars by category. It is related with a basic or full presence of EES components. ACEA (Association des Constructeurs Europeenes d´Automobiles) classifies the car model in five categories depending on their respective competit-ive market segments. These categories are the following ones: A (basic), B (small), C (lower medium), D (upper medium), E (executive).

Selection of cars by age range. It is related with the natural life span of cars and the assumption of reuse, recycling and recovery considerations by the EES com-ponent manufacturer. The recyclers set three categories: >15 years old (natural ELV category), from 15 to 5, and from 5 to present (premature ELV categories).

Selection of cars by highest selling rate in Europe. It is related with the interest of the EES component due to its abundance. The idea is to compile information from national car manufacturers associations and identify the car models with the highest selling rates in Europe.

Partners at this “EES recycling” workpackage consider necessary for determining recycling feasibility to provide physical examples of the EES components and information on sub-stance content. Additional information on composition, apart from the one obtained from the



studies of physical samples, will be request to car dismantlers, car manufacturers, EES man-ufacturers and different associations as follows:

Car dismantler and car shredders in the project (Metall Recycling and Müller-Gut-tenbrunn) for covering samples from ELV

EES Component manufacturer in the project (LEAR) for covering new specific components

Car manufacturer in the project (FORD), to cover new components from different EES component manufacturer

Contact with ACEA (or national associated branches, ANFAC – Spain, SMMT – United Kingdom...) and ask for composition of EES components and for informa-tion pertaining the European car sales in the different car categories in the years selected for study. Proposed contacting via FORD as ACEA member and request average data and/or range with upper and lower limits of the access to specific data is restricted.

The EES components have been classified in different recycling groups depending on the re-cycling processes to each one. The components have been classified in four groups. First group is the cables group that is nowadays well defined. In second place is electric motors and alternators group, these components will be recycled mechanically by IRSA because of the high presence of metals in their composition. The third recycling group is the board con-taining devices group, the components of this group will be recycled chemically by Rohm & Haas due to the presence of printed circuit boards in their composition.

The recycling processes of the components of these three principal groups are well defined but there are other components whose recycling processes are not defined because of their heterogeneous composition. After studying the composition and containing materials of these components, thanks to the study to create the database, the recycling processes to these components will be defined.

2.1.2 Study of physical samples of EES components.The work in Task 4.1 has been carried out studying the EES components via manual dis-mantling of parts, identification of materials and measurement of quantities. LEAR has sup-plied the following new EES components (from production rejection) for study:

Wire harness (SEES component group 3)

- Wire harness (passenger compartment, OPEL - Vectra)

Connection and protection devisces (SEES component group 4)

- Passive PCB junction box (passenger compartment, FORD - Focus)

Smart junction boxes (SEES component group 5)

- Smart junction box (passenger compartment, OPEL - Vectra)

- Smart junction box (engine compartment, OPEL - Vectra)

Integrated mechatronic components - IMC (SEES component group 6)

- Seat mechatronic (passenger compartment, FIAT)



- Electronic Control Unit for windows, sunroof... (passenger compartment, MATRA)

-

Müller-Guttenbrunn has supplied the following EES components from ELV for study:

Sensors (SEES component group 1)

- Lambda control exhaust gas sensor from EoL vehicle


- Wire harness from EoL vehicle

Connection / Protection devices (SEES component group 4)

- Passive junction boxes engine compartment from EoL vehicle

Motors / Generators (SEES component group 8)

- Starter motor from EoL vehicle

- Alternator from EoL vehicle

Entertainment (SEES component group 12)

- Cassette player / radio from EoL vehicle

Apart from these EES components that are grouped in the component groups defined previ-ously, different relays and fuses have been studied because these elements are presented in most of the junction boxes f the vehicle.

Relay from EoL vehicle

Small fuse from EoL vehicle

Large fuse from EoL vehicle

2.2 Developed data formatA data format has been developed to the study of the different EES composition and as-sembly systems. The structure of the template is detailed below and the different sections of the template are defined.

Thanks to the developed data format; the material composition, the material quantities and the second level disassembly steps of the EES have been learnt. The information obtained from the data format of the different EES will be used as a tool in order to focus the efforts on other workpackages.

The results obtained in this Task will be used in LCA, LCC and recyclability potential studies in order to determine the optimum recycling scenarios. In the same way, the information ob-tained from the database will be useful to define the Eco-Design Guidelines and to develop a new EES design for example integrating intelligent materials or redesigning the EES.

Dismantling of the parts and components from the ELV is defined as first level dismantling and is made by the car dismantlers and shredders to remove the EES from the car. Dismant-ling of the removed EES is identified as second level dismantling and is made by the re-cyclers to analyse the EES from the recycler point of view (components, fractions and materi-als) and to fill the database in this task.



2.2.1 File template for EESIt has been developed a file template in MS Excel sheet format to include EES components with the following structure. Format and aesthetic revisions pending.

1. CAR INFORMATION

Car category

Age category

Car brand

Car model

Manufacture year

Manufacture country

2. EES COMPONENT INFORMATION

Component group (previously defined in Table 1)

Component type

Position in car

Manufacturer

Model

Manufacture year

Manufacture country

Length (cm)

Width (cm)

Height (cm)

Total weight (g)

3. EES COMPONENT COMPOSITION

Component parts

Wire + connectors

Displays

Printed circuit boards

Batteries

Others

4. MATERIALS

Metal / alloy

Polymer / blend / composite

Others

5. MANUAL DISASSEMBLY STEPS



Time

Tools

6. MANUALLY DISASSEMBLED FRACTIONS

7. STATE OF THE ART RECYCLING SCHEME

Materials breakdown (seven groups as referred at standard ISO 22628:2002(E), “Road vehicles – Recyclability and recoverability – Calculation method”)

1. Metals

2. Polymers (excluding elastomers)

3. Elastomers

4. Glass

5. Fluids

6. Modified organic natural materials (MONM)

7. Others

Splitting of group 1. Metals

Ferrous metals (steel and iron)

Non-ferrous metals

- Light metals and alloys (Al, Mg, Ti…)

- Heavy metals and alloys (Cu, Zn, Ni, Pb, Cr…)

- Precious metals (Au, Ag, Rh, Pt, Pd…)

Splitting of group 2. Polymers (excluding elastomers).

Thermoplastic

- PET

- HDPE

- PVC

- LDPE

- PP

- PS

- ABS

- PA

- PMMA

- PC

- POM

- PUR

- Polymer composite



- Others

Thermoset

- Phenolic resin

- Urea resin

- Melamine resin

- Alkyd resin

- Allyl resin

- Silicone

- Polyester

- Epoxi resin

- Cross-linked polyurethanes

- SMC/BMC

- Polymer composite

- Others

2.2.2 Sample files in database

After defining the file template that would be filled for the creation of the database, one file template has been completed for each studied EES component. All the templates are in the Appendix 3 of this document.

Filled six files with LEAR samples (separated files)


- Wire harness (passenger compartment, OPEL - Vectra)

Connection and protection devisces (SEES component group 4)

- Passive PCB junction box (passenger compartment, FORD - Focus)

Smart junction boxes (SEES component group 5)

- Smart junction box (passenger compartment, OPEL - Vectra)

- Smart junction box (engine compartment, OPEL - Vectra)

Integrated mechatronic components - IMC (SEES component group 6)

- Seat mechatronic (passenger compartment, FIAT)

- Electronic Control Unit for windows, sunroof... (passenger compartment, MATRA)

Filled six files with MÜGU samples (separated files)

Sensors (SEES component group 1)

- Lambda control exhaust gas sensor from EoL vehicle




- Wire harness from EoL vehicle

Connection / Protection devices (SEES component group 4)

- Passive junction boxes engine compartment from EoL vehicle

Motors / Generators (SEES component group 8)

- Starter motor from EoL vehicle

- Alternator from EoL vehicle

Entertainment (SEES component group 12)

- Cassette player / radio from EoL vehicle

Filled three files with relay and fuses samples (separated files)

Relay from EoL vehicle

Small fuse from EoL vehicle

Large fuse from EoL vehicle

2.3 Conclusions

After characterizing the EES samples that have been selected as the best ones to the recyc-ling and filling a developed file template for each one, the results and data of these templates can define some general conclusions.

The studied EES components can be grouped in three groups according the recycling routes that can do taking into account the materials and dismantling steps that have been carried out:

Mechanical recycling: Cables/Wire harnesses (SEES component group 3) and Electric Motors/Generators (SEES component group 8) can be grouped in this “mechanical recycling” because more than the 90% of the material in these products is metal group 8 and more than the 50% of the material is cable in group 3. Cable fraction has a well defined mechanical recycling nowadays but motors and alternators have not a defined recycling route. Taking into account the high metal content of motors and alternators, the mechanical recycling is considered the best option.

Mechanical recycling plus chemical recycling plus plastic recycling: Printed circuit boards containing devices include in this recycling group. Printed circuit board containing devices are the following SEES component groups: Connection/Protec-tion devices (SEES component group 4), Electronic control units (ECU) (SEES component group 5), Integrated mechatronic components (IMC) (SEES compon-ent group 6) and Entertainment (SEES component group 12). In these cases after analysing the characterisation results, we can see that there is not a majority ma-terial fraction which defines the recycling process. In this recycling group, two are the main material fractions: plastic fraction and PCB fraction.

After analysing the characterisation the main conclusions of the SEES component included in this recycling group are the following ones:

Presence of PCB s: range from 35-55% weight (*)



(*) This share can be increased since attached components as fuses and re-lays, could be not present.

Material shift in housing from metal (old designs) to plastics (new designs)

Plastics materials for housings not standardised (ABS, PA or PP)

Reversible joints (screws, clips...)

Samples from ELV are dirt and damaged

Plastics predominate, on contrary G8 motors and generators >95% metals or G3 cables >50% metal

Taking into account the material fractions that are presented in this recycling group the proposed recycling route is a combination of mechanical and chemical recycling. Thanks to a first mechanical recycling the PCB fraction and the plastic fraction could be separated in order to treat then the two fractions in different re-cycling routes. The PCB fraction could continue being treated in a chemical recyc-ling in order to obtain the precious metal of the PCBs and the plastic fraction could continue being in a mechanical recycling in order to obtain recycled plastic fraction with the highest quality.

Chemical recycling. Sensors and actuators, like the lambda sensor, are included in this chemical recycling group. These components usually contain precious metals in slight quantity that can not be recycled mechanically, because of that the chemical recycling is the best option to recover the precious metals that are presented in these components. Palladium and Platinum are presented in the Lambda sensor for example.

2.4 Identification of Components for Chemical and Mechanical Recycling Studies

End-of-life vehicles contain an increasing amount of electronics which represents a growing proportion of the overall value of the car. Similarly, at end-of-life the electronics portion of the materials found in the overall scrap content of a car represents an increasingly valuable source of materials. There is clearly a need to develop new methods for selectively recover-ing these materials from the overall waste stream from end-of-life vehicles.

The three tiered assessment methodology undertaken within SEES project in “Integrated As-sessment of EES in Cars” report, identified fourteen different types of electronic devices that may be found in a modern vehicle each of these has a different material content and value. It is these inherent differences in material composition and value that have been used to de-termine the optimum treatment and recycling approach for each of the selected EES com-ponents.

Other important considerations in the selection process include; the available quantities of selected components produced by the disassembly studies and the fact there are already well established recycling and disposal pathways for some of the selected components. Ad-ditionally, the EES have been evaluated from a recyclers point of view enabling EES com-ponents that can be recycled using similar recycling technologies to be grouped together.



Table 1 summarises the recycling groups of EES defined at WP4 and the selected EES com-ponents in WP1 following the three tiered assessment process:

Filter 1: Determination of relevant and representative groups of components

Filter 2: Identification of most relevant components from selected groups

Filter 3: Component feasibility for SEES project that depends on considerations of partners from other workpackages.

A key requirement for the technical and economic success of any chemical recycling route will be the ability to source a suitable feedstock that is rich in the materials to be recovered and which consumes a minimum amount of chemicals during the recovery process. An effi-cient method will ideally also offer good material recovery selectivity in order to enhance the overall efficiency of the process. Consequently, electronic devices containing printed circuit boards (PCBs) such as active and passive junction boxes, radio cassette players etc. have been selected for evaluation under the chemical recycling study.

However, for the purposes of the practical trials to improve the success of the chemical re-cycling process from a commercial perspective will necessitate the integration of compliment-ary mechanical separation and comminution techniques applied at earlier stages of the re-cycling process so that a suitable feedstock can be supplied. The lambda control exhaust gas centres have also been selected for inclusion in the chemical recycling study. In common with PCBs these devices contain relatively high concentrations of precious metals (platinum) that make them desirable from chemical recycling perspective.

The cable, alternator and motor recycling groups have been grouped together and selected for discussion under the mechanical recycling studies. These components have a high volume of metals in their composition and their volume and mass precludes them from the chemical recycling studies.

The lead-acid battery is an important component with respect to achieving SEES objectives however, there are well established recycling pathways for discarded car batteries. Addition-ally, HID headlights also use established recycling and disposal routes. Expertise from Indu-metal as authorised recyclers for these components has been utilised in a theoretical over-view of current recycling methodologies. Another recycling group to be the subject of a the-oretical study of recycling techniques are liquid crystal display (LCDs) screens. These com-ponents used in vehicles to transmit navigational information to the driver or to provide enter-tainment for passengers are typically not in widespread use and the technology to recycle LCD modules at end of life is a new and emerging technology.



3 Mechanical Recycling

3.1 Identification of Available Technologies for Mechanical TreatmentSorting of materials (metals and plastics) of EES parts and components coming from dis-mantling and/or car shredding is a fundamental part of recycling because EES contains a number of metals that have to be separated from each other and from other contaminants to prepare for material specific recycling and give an added value.

The main steps in the mechanical treatment are the size reduction of the components and the separation of different fractions, avoiding cross contamination to give to each fraction the highest added value as possible. We will make an overview to the main size reduction meth-ods and sorting / separation methods.

3.1.1 Overview of mechanical recycling technologiesThe sorting of metals and plastics of EES components derived from car dismantling and / or shredding is a fundamental part of the mechanical recycling process. The main steps in this process are size reduction and the separation of different fractions avoiding cross contamina-tion.

Size reduction involves the use of equipment such as shear-shredders, impact-shredders, hammer mills, granulators and rotary grinders to reduce the different materials to specific size ranges. Shear shredders are appropriate for metals in cables or sheets and hollow plastic parts while impact shredders are usually applied for the destruction of electrical and electronic appliance casings. Separation equipment can be classified according to the type of material for example, dry and wet media or the material property that is exploited to achieve separation such as gravity, magnetic or electrostatic separators.

In the size and shape separation process, the separation of solids is based on their different sizes and shapes. Rotary screens (trommels) and vibrating screens that separate at least a coarse and a fine fraction are normal configurations. In gravity separation, the separation of solids is based on their specific weight and aerodynamic features. Separation tables use a vibrating movement and its inclined surface is continuously supplied with particles that are fluidised by a uniform pressurised air system that stratifies the light material to the top of the product bed and allows the heavy material to contact the table surface. The heavy fraction moves up hill, while the light fraction fluidised by the air system moves downhill. Pneumatic classifiers have an ascendant air jet that is used to remove light materials (foams) and lam-inar materials (films) from other heavier solids.

In density separation, the separation of solids exploits differences in aerodynamics/hydro-dynamic properties and density. Sink/float tanks give two solid streams, one denser than the liquid media that sinks and the other one lighter than liquid media that floats. Flotation cells make use of the fact that hydrophilic particles are moistened by water, whereas hydrophobic particles are moistened by oils and air bubbles; therefore, if air bubbles are introduced into aqueous slurry, the bubbles adhere to the hydrophobic solid particles. As a result, air-solid aggregates are carried out to the surface, forming a froth layer. The result is the separation of hydrophobic from hydrophilic particles. Hydrocyclones use the rotational motion produced by a suspension (water + material) entering tangentially under pressure. Inside the hydrocyc-lone, the heavy and light fractions are separated using centrifugal forces, and the geometry can be modified in order to achieve better purity. Shaking tables enable metals, minerals,



and chopped wire/plastics to be separated by means of this wet gravity-based separation method.

Magnetic separation enables ferrous metals to be separated from other solids using either temporal or permanent magnets in belts called “over bands” or drums. Eddy current separa-tion is used for non-ferrous metal separation, this method relies on the fact that eddy currents are induced in the conductive, non-ferrous particles due to the changing magnetic field. In-teraction between eddy currents and the magnetic field results in electrodynamic forces upon the conductive particles, and hence different trajectories for these particles and the non-con-ductive ones. Electrostatic separation, is based on electrical conductivity values (insulating or conductive materials) that are charged by corona discharge, induction or friction and are separated by attraction or repulsion.

Infrared heating separation combines infrared radiation to heat a stream of mixed thermo-plastics and compression. The mixed stream is irradiated to a point in which a single type of plastic is softened, but not melted. Following the infrared heating stage, the mixed plastic stream is fed through a compression system where the softened plastic sticks and is re-moved from the stream.

3.1.2 Size ReductionShear-shredder

Its function is the size reduction of plastic objects and cables to a smaller particle size more appropriate for subsequent recycling processes. The shredding action occurs between adja-cent discs and the degree of shredding is determined by the number of hoods on the circum-ference of the cutting disc and the width of the cutting disc. It is very convenient for all sorts of cable. Heterogeneous materials are ripped up and copper can be separated from plastics and others metals. From the plastics point of view, it can be considered adequate mainly for sheets and hollow plastic parts of EES.

Figure 1 A slow speed shear-shredder Hammer mill / Impact Shredder

Its function is the size reduction or pulverisation and the destruction of the appliance casing of electrical and electronic elements. The first step in the size reduction of electrical and electronic elements is the destruction of the appliance casings, making the diverse compon-ents accessible. A discharged grate placed below the rotor determines the size of the product.



In the case of most of selected EES components, seems to be in principle the most conveni-ent first stage of the process. The idea should be not to use any grate because the objective is not to reduce the size, but to get the plastic fraction separated from the PCBs.

Granulator

Its function is the size reduction of plastics objects or shredded material to a particle size between 2 to 20 mm. These machines employ a system of rotating knife blades. The plastic scrap is reduced in size by the cutting action between rotor knife and stationary bed knifes.

Wet granulation uses water in a combined cutting and washing stage. The cutting edges of the knife cutters are cooled by direct water.

Rotary grinder

A rotary grinder is equipped with steel blocks about 2.5 – 5 cm in size, mounted on a rotor. These steel blocks chip fragments from the incoming material as it is forced into the teeth by a ram. Rotary grinders thus produce a smaller particle size than conventional shredders.

3.1.3 Separation MethodsThe following separation methods will be described in this chapter:

A Processing by Dry Separation A.1 Gravity separation A.2 (Electro)magnetic separationA.3 Electrostatic separation A.4 Particle for particle sorting A.5 Image processing

B Processing by Wet Separation B.1 Rising current and hydro-cyclone methods B.2 Sink-float method B.3 Jigging B.4 Flotation methods

A Processing by dry separation

A.1 Gravity separation

A.1.1 Industrial Screening

Sieving or screening is the separation on the basis of size, with the aid of gravity. After breaking or shredding, the granulate is passed repeatedly over various vibrating sieves or screens to divided it into the different fractions required. Although there are various types of sieve the most common are shaking and vibrating screens, sometimes co

A.1.2 Centrifuges and Cyclones

Separation can be carried out with the aid of centrifugal force. This method is applied in vari-ous recycling sectors, and is among others used to remove oil from water and to separate granulates or powders and certain other substances in chemical processes from air. In dry separation systems, air has to be separated from the solid particles either to obtain the final products or to separate dust collected during the separation from air. Cyclones are widely used for the separation of solids from air.



A.1.3 Air Classification

Air classification can be used for resource recovery after shredding and the initial classifica-tion of feed materials. There are many types of air classifier on the market with different physical configurations, which can be divided into four basic categories; vertical, horizontal, inclined and rotary.

Vertical air classifiers are simple devices for the separation of materials mixtures with a relat-ively large difference in density, like plastics and metals.

Horizontal air classifiers are often used in combination with vibratory feeders. This process is applied for example for the output of an automobile shredder.

The inclined air classifier is frequently used in combination with vibratory feeders on a vibrat-ing screen. This combination of screening, inclined feeding and air suction, is used in glass recycling for the removal of plastics and paper stock form the cullet stream.

Rotary drum air classifiers are used for electronic scrap, among others, where heavy material has to be separated from light.

A.1.4 Friction Separators and Shaking Tables

For material mixtures with large differences in shape or density, the inertial or friction separ-ator is a simple device to pre-concentrate material or to generate end-products. The combin-ation of forces separates the lighter particles from the heavier ones.

Typical feed products are electronic scrap and cable granulate.

Figure 2. A shaking table for copper treatment at IRSA´s facilities

A.2 (Electro)magnetic separation

A.2.1 Magnetic separation

Magnets are the oldest aid to metal separation after hand sorting. Their specific use as an aid in identifying and separating ferrous and non-ferrous metals was discovered later. In gen-eral, magnetic separators can be divided into two groups. Low intensity and high intensity. In either case, the magnetic field can be obtained by permanent magnets or an electromagnet. In general, the high intensity magnetic separator is necessary in eddy current plants to pro-tect the equipment against mechanical damage.



A.2.2 Eddy Current Separation

In general it can be said that when a conducting object is passing across a changing mag-netic field, eddy currents will arise in the object, generating a magnetic field that opposes the field applied. Eddy currents can be generated in a conducting particle by changing electro-dynamic magnetic fields or by moving permanent magnets. Figure 3 presents a schematic of an eddy current separator.

Figure 3. A schematic of an Eddy Current Separator

A.3 Electrostatic Separation

Electrostatic separation is based on the principle that materials with different conductivity lose their charge in accordance with the extent of the receptiveness of an electric charge. In electrostatic separation, processed particles are charged with electrons, after which they move towards the positive and negative poles of the separator. The recycling industry util -ises two types:

Corona induced electricity where a high voltage is especially applied to charge non conduct-ing or poor conducting particles, for example for separating metals from plastics.

Tribo induced electricity where the shredded particles of various plastics collide against each other, thus charging each other according to the tribo electric sequence of polymers.

A.4 Particle for Particle Sorting

After size reduction to obtain the necessary liberation of metals and non-metallics, various mechanical separation processes can be applied to concentrate metals or other materials.

A.4.1 Metal Detection

The most simple metal detector is a coil around a belt conveyor which is stopped if metal is found to be present. For plastics with an already low metals content, the usual solution is a combination of transmitting and receiving coil and a mechanical valve, electrically or air activ-ated, which ejects the metal particle and some of the plastic with it.

A.4.2 Sensing Systems Based on Light

When particles pass under a light source, differences in colour, transmission, intensity, fluor-escence and other properties can be observed and measured. Most materials reflect light.



Only a few materials are translucent like glass and some polymers. There are many light sources available: electric bulbs, fluorescent lamp, Xenon lamps, ultraviolet lamps and a vari-ety of gas-filled lamps with various emitted light spectrums. Lasers emit one or only a few spectral lines. The reflected light can be collected with a detector by one diode or a camera. The different sensing systems are able to measure the reflected light of a material or the transmission of light through a material. The light sources used for these measurements de-termines not only the spectrum which is radiated but also the spectrum which can be reflec-ted or transmitted.

A.5 Image Processing

Using a camera as a detector in combination with a computer, a product on a belt conveyor is scanned picture-for-picture, or frame-for- frame. Assuming a belt conveyor is 1 metre wide and running at a speed of 1 metre per second, the images taken with a standard 3:4 black and white or colour camera will be 1 metre wide and 0.75 metre long, each 0.75 sec. One frame will have to be seized and processed by a computer. The position of each item on the belt running at a constant speed can be defined by a combination of an impulse counter on the side of the belt and the synchronisation of the camera with the computer. After pro-cessing each image, the computer will activate the air valves of the ejection system for the removal of identified particles, which, for example, can be brass particles in a copper product.

B Processing by Wet Separation

B.1 Rising Current and Hydro-Cyclone Methods

In rising current a continuous rising column of water is projected through a pipe. The feed material to be separated is introduced in the rising column of water. The material which sinks faster than the water column rises, falls to the bottom of the separator. The material trans-ported by the column of water is then separated from the water by a screen or a sieve. The water can be reused in the process.

In hydro-cyclone separation water, or a heavy media suspension sometimes called “ heavy water”, is brought into rotation in a piece of equipment which is a combination of a cylindrical and a conical part. As a result of the rotation, larger and heavier particles first move to the wall and then sink along the wall to the underflow or an apex in the bottom. Lighter, or smal -ler, materials will remain suspended and leave the cyclone via the overflow of vortex at the top of the cyclone. This method has been adapted to separate metals.

B.2 Sink-float Method

The method sink/float in water or another liquid can be found for the separation of plastics, making use of the fact that they have different specific weight. The sink/float in a suspension of water and a solid material method is used particularly for the separation of shredder alu-minium and magnesium from a non-ferrous mix. It is based in the principle that the material we want to separate have different densities.

B.3 Jigging

Jigging is one of the oldest methods of gravity concentration. The jig is generally used to concentrate relatively coarse materials down to 3 mm. When the feed is fairly close sized it is no difficult to achieve a good separation at low cost. In the jig the separation of materials



of different specific density is accomplished in a bed which is rendered fluid by a pulsating current of water.

This method is very similar to the rising current separation process, but here the jet of water is projected through the screen in pulses.

Jigging is used to separate shredded metals and particularly to separate plastics from metals.

Figure 4. A schematic of jigging

B.4 Flotation Methods

Flotation methods are used in some cases to separate various plastics. Air bubbles are intro-duced into the suspension from the bottom of the flotation cell and will selectively adhere to the particles to be recovered. The foam with the material to be recovered can be collected at the top of the flotation cell.

3.2 Testing and Demonstration of the Technologies for Mechanical Treatment

The future reuse and recycling targets that the European Directives 2000/53/EC fix to the End-of-Life Vehicles require the improvement of the actual recycling scenario. The specific recycling of the automotive electrical and electronic systems (EES), that in the most of the cases are not recycled nowadays, can be a good advance to achieve this recovery/reuse tar-gets. The demand of more services and functions in the cars has increased the EES contain in the new cars, and the trend in the nearest future will continue.

Taking into account the wide variety of different components, component size and weight and the composition of these ones is necessary to concentrate the efforts in the recycling of some specific EES considering legal, economic, dismantling and recycling aspects. After analysing



the different EES and the different aspects, the some EES components have been the chosen as more appropriate ones to study .

3.2.1 Mechanical Processes for Recycling EES Components

The first step from the recycling point of view is to select and classify EES components de-pending on the recycling potential which is directly related to the content of the different com-ponents that could be recycled using existing circuits. In order to optimize the revenue that the dismantler could obtain from devices (content on valuable materials like copper, precious metals etc.), and the best available technology for each group of components, different pro-cesses have been defined:

Printed Circuit Board Containing Devices

Seat mechatronic

Passive PCB Function Box

Passive smart junction box

Cables and wire harnesses

Electric Motors and Alternators and a Mixture of Other Devices

Alternator

Sensor lambda

Passive Junction Box

Radio

Starter engine

These all groups will be studied in detail within this report .

3.2.2 Mechanical test for junction boxesWe have received two different streams of Junction Boxes, rejects from production line (LEAR) , and from end of life vehicles (Müller- Guttenbrunn)

In principle was planned the same process for both streams but during the shredding step, we realized that the junction boxes from Mügu have no printed circuit boards inside. However the metals content is pretty higher in these junction boxes. This makes necessary a change in the previous process in order to optimize the metals recovery.

Figure 5 Junction Boxes from Lear



Figure 6 Junction Boxes from Mügu

According to this first approach, the objectives for both streams are , on one hand to get plastic fraction without other cross contaminations to be treated within plastic recycling stud-ies, and on the other hand, to get, either printed circuit board or metallic fraction, free from plastics and others to get the best market and value for them.

To achieve these objectives, IRSA has developed an own process for each stream.

During previous steps, we proposed a scheme for the treatment of these components. With the last tests carried out and in a bigger scale, the schemes and process have been updated. Tests have been carried out at Indumetal Recycling facilities in Spain with the material re-ceived from Lear and Mügu. Lear sent to our plant 176 Kg of junction boxes and Mügu 53 Kg.

Both streams have been treated separately at IRSA plant trying to adjust the capacity of equipments to smaller quantities but, fulfilling all the specifications that each fraction obtained requires to be incorporated in following processes.

Figure 7 Plastic fraction for WP5

In the case of plastic fractions that will be studied within plastic recycling and PCBs for chemical recycling, the specifications are the reduction size and avoid other contaminations. After checking and characterization of the plastic fractions obtained, the metal content is lower than 0.5 % in both cases.

The magnetic fractions are sent for steelworks. In this process other elements like cooper, aluminium or zinc are not welcome and you obtain different penalties depending on the con-tamination of the fraction you are sending. However, it is necessary to explain that this kind of metallurgical process is quite flexible and you hardly get a penalty if levels of contamina-



tion are low. However for copper smelters, the restrictions and limitations are higher. Further-more, small variations of other elements in copper, change the price value of the fractions drastically.

Figure 8 PCBs for chemical recycling

Rohm and Haas is studying the chemical recycling of printed circuit boards fraction. We have prepared this fraction coming from junction boxes from Lear. Our objectives have been to get the proper size of the material to achieve the best separation of the material avoiding the contamination of plastics and other metallic components and reduce to a suitable size for fol-lowing chemical studies.

This fraction is also well accepted in copper smelters who, depending on the purity of the fraction, can introduce the material in the different steps of the process.

As stated below, we have tested different schemes for the treatment of junction boxes to re-cover the different valuable fractions. We indicate also the percentage of the recovered frac-tions and the composition. Some of these percentages are estimations since, some of the fractions are too small to be treated in our plant.

Some of the fractions have been prepared to be analysed by Alex Stewart. The elements that have been analysed are copper, silver, gold, palladium and platinum because have the deep-est impact in price value for copper smelting process and, on the other hand the way to pre-pare the sample for analysing (smelting process around 1000ºC), make it lose other ele-ments like aluminium, iron, zinc and others. For analysing other elements, more quantities for preparing samples would be required.

Next scheme shows the mechanical recycling process proposed for Junction Boxes from Lear at IRSA facilities.



Figure 9 Mechanical recycling process proposed for Junction Boxes from Lear

In the previous scheme is shown the process followed at IRSA facilities for Junction boxes from Lear. The power consumption appears in the pink rhombus and is referred, in the case of the first line to an input of 600 Kg / hour, and for the second line to 1500 Kg/ h.




For size reduction and liberation of the material are used two blade shredders. After these two shredders a screening separates material over and below 10 mm. Material over 10 mm is sent to an Eddy current separator to get different fractions. With the overband is separated magnetic fraction for steelworks. The percentage is 6.37 % and the 97 % of the fraction is iron. Others are plastics, and metals joined to the iron.

The recovered plastic fraction from Lear means around the 34.09% and is sent to Gaiker for further studies. The printed circuit board fraction (Figure 8) means around 33.52 % and is sent to Rohm and Hass for chemical recycling studies.

The 26.02 % , material under 10 mm, is reduced to around 5 mm and, using the vibrating movement and inclination of two separation tables, are separated two different metallic frac-tions with different contents on copper and precious metals for copper smelting processes, and a plastic fraction for plastic recycling studies.

Figure 11 Fraction under 10 mm

In both metallic fractions there is some plastic coming from the housings of junction boxes but also, epoxy from boards and other elements that have not been analysed.

This scheme can show a view of one possible process and some recovered percentages. Of course, there can be other many possibilities for this kind of treatments. It is necessary also to have into account that tests have been carried out with small quantities of material and it has been necessary some assumptions. With more material to be tested , the results would be more precise.



Next scheme shows the mechanical process for Junction Boxes from Mügu.

Figure 12 Recycling Mechanical process for Junction Boxes from Mügu

The same methodology has been followed for Junction Boxes from Mügu. The main different between both components is the content of printed circuit boards. After Eddy Current separa-tion we realize that the metallic fraction containing in this kind of components was different from the previous one and that different steps for treatment are needed.



Figure 13 Fraction over 10 mm

For this reason, the metallic fraction over 10 mm that is a mixture of plastics and metals , to-gether with the mixed fraction under 10 mm are treated in the second line.

The process through second line is similar to the followed by junction boxes from Lear. Shredding for size reduction and separation in densimetric tables.

The fractions we have obtained with this material are very small, since the input was around 50 Kg. This is the reason why we are not able to analyse all the elements containing in the metallic fractions. To send to the lab to analyse copper and precious metals we have to pre-pare the samples and, during the smelting process some elements like aluminium , iron and others are lost.

We have done a first approach to a mechanical recycling process for this kind of material. Our first objective was to get the plastic fraction and the printed circuit boards for studying in other tasks. For this purpose we have found the most suitable size and process but there are some other metallic fractions that could be developed.

Some of the particles have a very small size and for this reason, there are more losses in the filter systems. Another added problem is that the quantities we have been working with, do not allow us to calibrate and adjust the equipment in the best way. For this reason there are some fractions that require more and deeper studies.

From the technical point of view the mechanical process is solved, and the fractions for chemical treatment ( printed circuit boards) and, plastic fractions for recycling studies have a very good quality since there are no cross contaminations with other fractions.

From the economical point of view, the metallic fractions obtained need more development to get a better price for them. These kind of fractions can be mixed with other materials that make them more interesting, from the economical point of view, to be grinded and separated again and get better prices from copper smelters.



3.2.3 Mechanical test for wire harnesses

Figure 14 Recycling Mechanical process for Wire Harnesses from LEAR



Figure 15 Recycling Mechanical process for Wire Harnesses from MÜGU

The two previous schemes show the process developed for wire harness treatment. In prin-ciple the idea was to treat this material in the specific cable plant at IRSA facilities, but the in-put was not enough to get a good stabilization of densimetric tables. For this reason we de-cided to change the first scheme proposed and use other equipments, more suitable for the quantities we were going to treat. Anyway, the principle of the process is exactly the same.



Figure 16 Wire harness from Lear

The consumptions of the equipment are referred to an input of 1500 Kg/hour and are re-marked in the pink rhombus in the diagrams.

The initial input are two different batches of wire harnesses, 233 Kg from Lear and 223 Kg from Mügu. Both batches have been treated following the same process since the features are very similar. There were two main objectives, to get a fraction of plastics without metals to be studied within plastic recycling studies and, the best valuable copper fraction as pos-sible.

It is necessary to have into account that the price of copper depends on two main factors:

The purchasing formulas applied by each Copper metallurgy processor, which tend to vary at regular intervals.

The quoted price of the metals which at times may be subject to major variations.

In this case we have also analysed copper and precious metals. The reason for this is the dif-ficulty of preparing samples for analysing all elements, since some of them are lost due to the high temperatures. We have assumed that the limit of the price is going to be the cooper con-tent (around 96%) and no other impurities like lead, tin, aluminium, zinc, iron and nickel. In copper price, any element in high percentage, even precious metals, have a negative influ-ence.

This fraction is sent to copper smelting process where is introduced in anode furnace step or even electrolysis, depending on the concentration, improving the productivity of the whole process.

The copper metal processing has four main steps; shaft furnace, converter, anode furnace and electrolysis.



Figure 17 Cooper fraction

Mechanical treatment allows the entry of concentrated raw material in advanced stages of the metallurgy process, making it possible to optimize costs and yield in Cu metallurgy, and allowing for savings in time, energy, materials, maintenance and increases in capacity and metal yields.

Plastic fraction have been sent to Gaiker for recycling studies. The metal content in this frac-tion is very low, even less than 0.5 %. This fraction is a mixture of plastics , mainly polyamide , polyolefin and others that due to the size does not seem very easy to treat.


There is another fraction called metal + plastic. In this case the copper content is quite low so, the way for this kind of fractions is to put together with other similar and continue the pro-cess of grinding and separation with densimetric tables. In this case, the process is not either optimized since our objective was to get the best plastic fraction, and that means with the lowest level of metals on it. The process proposed is the right one, but further developments are required to improve the process from the economical point of view.

There is another fraction called metal + plastic. In this case the copper content is quite low so, the way for this kind of fractions is to put together with other similar and continue the pro-cess of grinding and separation with densimetric tables. In this case, the process is not either optimized since our objective was to get the best plastic fraction, and that means with the lowest level of metals on it. The process proposed is the right one, but further developments are required to improve the process from the economical point of view.



3.2.4 Mechanical test for EES mixed fraction After processing the junction boxes and wire harnesses, and analysing the results, was de-cided to study the EES mixed light fraction coming from car shredders.

This is for car shredders a final fraction that can not be treated anymore in their facilities if they have not a special treatment plant for these fractions.

For those companies with treatment plants similar to Indumetal Recycling’s ones, is a very in-teresting fraction. Here can be treated giving a high added value to the different obtained fractions. It is necessary to have into account that this fraction contains around 25 % of metals.

Figure 19 EES mixed fraction

IRSA has prepared a big scale test with 5 Tons of this material. Initially the material has been analysed and characterized to get all the information about the sample that is going to be processed. Furthermore, before processing the material, is necessary to study its behaviour to adequate and optimize all the parameters of the process.

The first step has been to prepare a representative sample and send to the lab for analysing. As has been commented before, the way the representative sample is selected, and the ana-lysis done is very important in this business.

Figure 20 EES mixed fraction



Usually the purchase/sale price is based on a formula and it is fixed depending on the results obtained. That is why all the companies prepare very carefully this step, and it is essential in this business.

Composition and characteristics of the initial sample

The average composition of the light mixed fraction is the following:

Figure 21. Average composition of the light mixed fraction

After this first approach the metallic fraction was prepared and sent to the lab for analysing. The main elements have been selected although there could be other minor metals in the sample, but only traces. The result is shown in the following Table 2:

Table 2. Main elements in metallic fraction

METAL CONTENT IN THE SAMPLE

Copper 17,99 %

Iron 5,21 %

Aluminium 1,76 %

Silver 246 ppm

Gold 2,99 ppm

Palladium 1,19 ppm

Platinum 1,19 ppm

After this first study of the composition and characteristics of the material, some tests were carried out to define the possible process to follow with this material.

In the following scheme is defined a simplify overview of the proposed treatment process for this EES mixed fraction.



Figure 22 treatment process for EES mixed fraction

This scheme has been named “simplify scheme” because the process is much more complex and are identified twelve different fractions in the process. All this fractions come because of the recirculation of some of them to get higher quality. However the principle is the one shown in the previous diagram.

Seven of these fractions are considered as the metallic ones for sale. Five of them are con-sidered plastic or dust from filters and cyclones.

The seven ones for sale are metallic fractions and are based on the iron, aluminium and cop-per and precious metals content. During the process are separated and is possible to obtain different qualities, with different concentrations and price, of course.

This is something that each recycler has to do depending on the kind of installation, ma-chinery and material to treat. The point is to find a balance between the cost that means to have more treatment and the profit you get from the fractions.

Metal fractions for sale

That is why we have identified seven different fractions for sale: Iron, aluminium, mixed metals, fine copper, copper-iron with precious metals, precious metals laminates, copper with precious metals. These fractions mean about the 43% of the total, because always contain some impurities and non metallic materials.



Following are shown different photos of the metallic fractions for sale. Below we will show a complete chart with all the fractions, analysis and estimated prices.

Figure 23 - Precious metals laminates-

The objective is to have an idea of how the process works, an estimation of the possible frac-tion, the quantities and their value.

Here are shown some examples of the different metal fractions.

Figure 24 Fine copper- Figure 25 Mixed metals

Figure 26 Cu-Fe with precious metals

These fractions are sent to metallurgical process: steelworks or copper smelters. Usually the price is based on a formula and for that reason, from each fraction is taken a representative sample and is sent to the lab to analyse the copper and precious metals content.

According to these lab results are fixed the prices. There are some fractions like iron that have normally the same prices with no significant changes.



Fractions for management

The same happens for non metal fractions. These mean the 57% of the weight and are re-covered in different steps of the process.

It is necessary to have into account that all the process has different exhaust and ventilation systems. For this reason is possible to find, not only the final plastic fraction but also, other fractions with dust from the filters and cyclones, and other organics.

The advantage of being able to recover and recycle the plastic fraction is clear. Not all these fractions would be suitable for this purpose, for example, the dust and sludge from filters and cyclones. These fractions have to be sent to a hazardous waste authorized manager.

However there is a very important fraction (36.72%) that contains different kind of plastics and rubbers. Nowadays is sent for energy recovery and coque substitution to a cement plant, but of course the best would be, to be able to separate the different polymers and recycle it into new plastics.

Other added problem in this EES mixed fraction is that, although the printed circuit boards presence in this material is very low, the metal they content is very low and for this reason, are recovered directly in the plastic fraction. This mixture makes more complex the plastic re-cycling.

Below are shown some of the photos corresponding to these fractions.

Figure 27 - Dust and impurities from filters and cyclones-

Figure 28 Dust and impurities from filters Figure 29 Plastic fraction for WP5 and cyclones



Summary table of the process

In the following chart is shown a general summary of all the fractions of the process. The data recovered are: the analysis of the input, the percentage in weight of the outputs, the composition of each and, the price estimations. There are other some internal data not avail-able since they have no interest for the project and would make things more difficult to under-stand.

The estimated prices are based on the analysis and the market actual prices. In the case of plastic we have assumed 0 €/T, in the case they are sent for energy recovery. If we are able to develop a way to recycle them, it would become a positive value.



Figure 30 Summary table-



It is possible to give an added value to these fractions that can not be optimized at car shred-ders plants. With a mechanical treatment is possible to get more concentrated fractions. These concentrated raw fractions are introduced in advanced stages of metallurgical pro-cesses.

The added value is enough to pay the mechanical treatment costs. Furthermore, it is possible to recover some other fractions like iron and aluminium that otherwise, are lost in copper smelters.

The plastic fraction that means the 36.72 % is a quite important fraction. Nowadays is sent to a cement plant for energy recovery and coque substitution. That means no revenue but no cost in the balance.

The process would be more profitable and attractive if we would be able to separate some of the polymers, to be recycled. That would mean to potentially recycle around 80 % of the in-put.

3.2.5 Mechanical test for motors and alternatorsFollowing with the study of the identified EES components was decided to test 250 Kgs of al-ternators and motors from end of life vehicles. The reason for the study of this fraction is be-cause copper coils and magnetic iron cores, are the major source of copper contamination in steel fraction at the car shredders.

The goal was to study, if a previous dismantling of these components, make possible to re-cover the copper from coils and iron fraction, free from contamination.

The suppliers to get material to prepare the tests have been local dismantlers. One of the comments received is that they are not very interested in this kind of activities, even if they are paid for it.

The reason for this is that, it takes them a long time to remove the components from the end of life vehicles. From the contacts we have kept, the only way to make possible the dismant-ling is developing designs or materials that make it easier and quicker. That has already fore-seen within SEES project.

In these two photos are shown some examples of the material and the separation and classi-fication of the material at local dismantlers.

Figure 31 View of the material at local dismantlers

SEES – Sustainable Electrical & Electronic System for the Automotive Sector of of 247


Motors

The hammer shredders at IRSA facilities, and most of them present in secondary shredding plants have two limitations: the size and the hardness of the material.

In the case of motors there are nearly no chances. The best way the lines in the plant can run is if motors are removed directly before entering the line.

The problem for this kind of components is that usually are quite big and hard, and this is a problem for the shredders. This can cause problems in the first hammer mill.

Another added problem is that the external housing is hit by the hammers and become a ball, with the copper coil inside. In this way it is not possible to recover the copper from the coil.

These “balls” are sent directly to metallurgical processes, where they are not very well paid, or to other plants with other separation methods, like media separation.

Figure 32 Example of the “balls”

Having into account all these aspects, either big motors or small ones are a difficult fraction for our process. From the point of view of metals recovery, it has no sense to remove these components and send to a mechanical recycling plant. From the point of view of process, could be necessary to remove the motors to protect the shredders.

Alternators

In the case of alternators it is nearly the same. For the big pieces it is not possible any treat-ment in the shredders.

There are some possibilities with small alternators, but the effort to recover and classify them is so high that, for us, from the technical point of view, has no sense to separate.

The main idea for the recycling of alternators is that the big ones have to be separated from the stream and send directly to a metallurgical process, because otherwise can cause dam-age in the shredder. The small ones can be treated in the line but, although the problems are less than in the case of small motors, the separation of the copper in coils is more difficult and problematic.



Figure 33 Difficult component for a mechanical separation

For this reason, the mechanical recycling is not the best treatment process for alternators in general.

Figure 34 Material after mechanical treatment

3.2.6 Battery RecyclingFirst of all the electrolyte is removed from the batteries The rest of the battery is shredded in the convenient shredder with a drain at the bottom where the liquids are collected and sent to an authorized manager.

The output of the shredder goes directly to a water bath where the polypropylene PP floats and is separated from the rest of the fractions. The plastic fraction PP is cleaned and sold for mechanical recycling. The rest of mixed fractions are sent to a metallurgical plant for lead re-covering.

This fraction is introduced in the smelting furnace with a reducer (coque coal or lignite) and Sodium carbonate (Na CO3). At about 500 ºC the lead Pb is extracted and recovered from the furnace. The remaining slags are sent to an authorized manager.

3.2.7 HID Lamps RecyclingThe lamps are considered hazardous wastes since they use mercury for running. The plants for treatment of this kind of waste are fully automatic and easy to operate. The versatility of these plants allows the processing of various types and sizes of mercury lamps, separating



the lamps into soda lime glass, aluminium end caps (in case they have), lead glass / ferro metal components and phosphor powder.

The entire process is incorporated in a container, in which the air is brought to sub-pressure. Thereby preventing mercury from being released into the environment, as exhaust air is con-stantly discharged through the internal carbon filters. The phosphor powder is separated from the by-products in different steps, which is one of the reasons behind the excellent pur-ity. This is done in an air transportation system. The mercury bearing powder is collected in distiller barrels beneath the cyclone and the self cleansing dust filters. All these plants have also to meet the strictest standards for purity and low mercury residue values. The re-covered products have a secondary market value.

All the process is based on hammer mills, sieves, non ferrous separation systems and ex-hausting systems in order to get soda lime glass used for new lamps, but limited for other us-ages; phosphor powder to recover phosphor when the mercury has been removed in the dis-tiller; aluminium caps and iron powder for metal recovery.

3.2.8 Liquid Crystal Display (LCD) RecyclingLiquid Crystal Display (LCD) devices find application in vehicles as an interface to communic-ate information to the driver from other electrical and electronic components such as the satellite navigation system or the engine management system, other uses include providing entertainment (DVD, video) to passengers. An example of LCD passenger entertainment is as shown in Figure 35. Currently, LCD devices are restricted to the top-of-the-range models however, the demand from consumers for in-car entertainment and multimedia systems pre-dicts a reasonably strong, mid-term growth for LCD modules. Consequently, there is a clear need to develop suitable recycling techniques to treat future quantities of LCD waste from automotive applications.

Depending on the function, a LCD device is typically comprised of the following components; plastic housing, a glass or transparent plastic screen, a back light, a printed circuit board, cables and a LCD panel. More specifically the LCD panel may described as two plates of a special, non-alkali glass with connective polymers (polarizers, colour filters, and protective films). The glass is plated on both sides with transparent electrodes usually made from in-dium tin oxide (ITO). These two glass plates sandwich a sealed, liquid crystal mixture which characteristically may contain twenty-five or more different liquid crystal compounds. It is this complexity in material use and structure coupled with the heterogeneous nature of the liquid crystal mixture that provides a partial explanation for some of the difficulties associated with recycling end-of-life LCD panels. Currently, there are very few available technologies that are capable of treating these devices, a situation that is likely to improve significantly with the im-plementation of the Waste Electrical and Electronic (WEEE) Directive. The WEEE Directive is a producer responsibility Directive that aims to reduce the environmental impact of certain categories of electrical and electronic products at end-of-life by establishing recycling and re-covery targets and by setting treatment guidelines for end-of-life operators. The Directive sets specific treatment requirements for LCDs with a surface area greater than 100cm2 and those that use a gas discharge lamp as a back light requiring their removal from WEEE and separate treatment. Whilst this legislative requirement does not extend to LCDs in automot-ive applications the fact that the directive’s requirements on LCD treatment has driven R&D in LCD recycling processes will have a significant influence on the future treatment and dis-



posal of automotive LCD devices. Annex 1 of this report presents a table that provides an overview of recent patent applications in respect of LCD recycling and recovery techniques.

In a theoretical evaluation of the reclamation process for recovering liquid crystal mixtures for reuse in LCD applications Martin, Simon-Hettich and Becker (17) report there to be no com-mercial benefits. Since the reclaimed LCD mixtures could potentially yield up to 500 different liquid crystal components, requiring separation and purification in order to produce ‘electronic grade‘ liquid crystals for use in LCDs. A process that is prohibitively expensive compared to the synthesis of new liquid crystals.

Figure 35 LCD device in a vehicles

A literature review of available LCD recycling techniques reveals that most processes focus on the recovery of the LCD glass as a substitute for silica in various manufacturing and incin-eration processes. The Electronic Industries of Japan under the Mechanical Social Systems Foundation conducted a survey in 2000 (18) of existing glass recycling technologies and in-vestigated the economic feasibility of substituting LCD glass in these processes under differ-ent recycling scenarios. The emerging LCD recycling technologies highlighted in the report include :

A technology for reclaiming glass substrate which involves the chemical separa-tion of all or a proportion of the colour filter, polyimide and electrodes from defect-ive LCD glass enabling the glass to be reused in the LCD manufacturing process

A methodology for the utilisation of silica rock as an alternative material in non-fer-ric refining using a process that substituted crushed LCD glass for silica rock in zinc recycling. Silica rock is used as an iron removal agent in recycling zinc con-tained in steel mill flue cinder

A technology under development for manufacturing tiles using waste LCD glass. The project aims to substitute waste LCD glass as a substitute for feldspar in a measure to lower the firing temperatures in tile manufacture

Technology for the reutilisation of soda-lime involved a collaborative project between a metal recycler and a glass manufacturer which utilises a temperature controlled decomposition process to enable the separation of components. The chemically treated cullet could be potentially recycled into other glass products.

The authors of the JEITA report found that substituting LCD glass for silica rock in zinc recyc-ling operations offered the most cost-effect recycling scenario.



As the largest global manufacturer of LCDs Sharp has become an established frontrunner in the development of technologies for recycling LCD modules. Although Sharp has focused its activities on recycling LCDs recovered from consumer electronic products and LCD panels from manufacturing waste, its recycling activities are reported here since they represent op-erational and/or state-of-the-art examples of LCD recycling.

Since 2000 Sharp has been recycling LCD glass at one its Mie manufacturing plants. Work-ing in collaboration with the INAX Corporation, Sharp have developed a technology that is capable of converting waste LCD glass into a raw material that is suitable for manufacturing tiles (18) The process involves crushing the waste glass into a sub 2.5 mm size fraction, and then mixing the pulverised glass with clay and feldspar and wet ball-milled to produce a slurry. The slurry is dried with a spray drier to produce a fine powder which can then be moulded into tiles and fired in a kiln at temperatures of 1250°C. The plant recycles approx-imately 30-50 tonnes per month of waste LCD glass using this technology.

In 2001 Sharp initiated a programme to develop technologies to recycle the plastic chassis and PCB components of their LCD modules (18) As a consequence of these activities Sharp purport to be able to recycle 70-80 per cent of the original weight of the LCD module. The plastic chassis can be successfully recycled into plastic pallets and wood substitute stakes, the precious metals recovered from the PCBs and the glass fibre fraction converted to slag and reused as a raw material in the production of cement. Additionally, Sharp have drawn to-gether a cross-divisional team to work in collaboration with the Japanese Electronics and In-formation Technologies Industries Association (JEITA) in developing further recycling techno-logies for LCD products and related materials. The project will consider eco-design, material types, smart materials to aid disassembly, separation studies and materials recycling and re-use. It is anticipated that a recycling programme will start in 2005.

In Europe the EU funded Liquid Crystal Display Reuse and Recycling (reLCD) Project aims to identify a cost effective and fast test methodology to verify if discarded LCDs are in work-ing order and to develop a technology to refurbish working LCDs. Additionally the project partners will develop an eco-efficient disassembly and recycling technology for the redundant LCDs.

3.3 Copper metallurgyThis section discusses some general ideas about copper smelters, the process and how to affect the different contaminants. At the end, mechanical treatment allows the entry of con-centrated raw material in advanced stages. The added value must be sufficient to pay the mechanical treatment costs.

One notable advantage of the mechanical process is that it allows the recovery of Fe and Al as metals and not as silicates or aluminates in the slag generated by copper ovens. If EES components have significant Fe or Al, which may be relatively frequent in relatively older designs, it is worthwhile carrying out mechanical pre-treatment to separate these two metals, which have a market value, unlike in copper processors where they are not valued or even rejected above a certain percentage.

The mechanical process is actually a pre-treatment for the copper metal processing. The im-purities that accompany the material with a low metal content may be removed up to a cer-tain point in the smelting furnace that heads the metallurgic process for copper, but this wastes a significant part of the energy contained in the plastics and reduces the productivity of the whole process. In the end a smelting furnace may almost operate like an incinerator,



but it is not designed for this purpose and does not recover the energy it emits into the atmo-sphere. It will also form a bottleneck making the rest of the process inefficient. However, mechanical pre-treatment, as well as recycling Fe and Al directly as part of its economic cycle, allows plastic concentrates to be obtained that may be of use as alternative fuels in nearby installations (incinerators with energy recovery, cement works, etc.) without the need to travel halfway across Europe to find a copper metal processor. Mechanical pre-treatment, where in most of the cases will offer benefits, also when considering the impact of transporta-tion, economic impact and environmental impact.

Figure 36. Copper smelter main stages and recovery rate

In the following Table 3, are shown the different elements that interfere in copper metallurgy, limits and problems that can be found:



Table 3. Different elements that interfere in copper metallurgy

AceptableEconomical moderate Penalties

High Penalties

Maximun limit permited

Radioactive elements Process contamination.Airborne and Environemnt contamination. - - - 0Asbestos Airborne contamination - - - 0Explosive materials Explosions risk - - - 0Thallium Airborne contamination - - - 0Cr ( 6+) Underground water contamination - - - 0Cyanides Underground water contamination - - - 0Polichlorbyphenils Dioxines generation on process - - - 50Aluminium+Magnesium Higher production slags. Al and Mg losses. < 50.000 > 50.000 - ?Antimony - smelter1 Toxic oxides.Contaminant Zn oxide < 100 - > 100 500Antimony - smelter2 Toxic oxides.Contaminant Zn oxide < 1.000 - > 1.000 10.000Arsenic - smelter1 Toxic oxides. < 1.000 > 1.000 - 2.000Arsenic - smelter2 Toxic oxides. < 1.000 > 1.000 - 10.000Berillium oxide Very toxic on particles < 5 - > 5 10Berillium alloyed Risk of BeO evolution on smelting < 200 - > 200 no dataBismuth - smelter1 Expensive impurity to remove most smelters.Cu became britle < 10 - > 10 100Bismuth - smelter2 Expensive impurity to remove most smelters.Cu became britle < 100 - > 100 no dataBromine - smelter1 Dioxines; Corrosive gases; metal wear < 3.000 > 3000 - no dataBromine - smelter2 Dioxines; Corrosive gases; metal wear < 5.000 > 5000 - no dataCadmium - smelter1 Toxic oxides no data - no data 10 to 50Cadmiun - smelter2 Toxic oxides no data - no data 10.000Chlorine -smelter1 Dioxines; Corrosive gases; metal wear. < 1.000 > 1.000 - 20.000Chlorine -smelter2 Dioxines; Corrosive gases; metal wear. < 2.500 > 2.500 - 20.000Chromium (non 6+) Higher production slags. Cr Metal losses. no data no data - 50.000Cobalt As Iron oxidaze and go to slag; metal lossesCopper Main objetive of Copper smelters > 100.000 - - 98%

Fiber Glass (SiO2) SiO2 necessary additive for good slag. High wear of shreders.Silicosis - - - -

Fluorine - smelter1 High corrosive gases < 300 - - 300Fluorine - smelter2 High corrosive gases < 5.000 > 5.000 - no data

Iron With cok, very good co-reductor agent in melting Cu. Metal losses. < 500.000 - - -

IndiumLead Pb emissions. Contamination final residues. < 30.000 > 30.000 ? - 5% to 10%Manganese Wear shaft/blast Cu lining and go to slag. Metal losses - - - -Mercury Toxic vapors < 2 - - 2MolybdenumNickel Reduce ductility of Cu. Eficient removal on a good electrolysis < 20.000 > 20.000 - 50.000

Organics and plastics

Tolerated co-reductor agent in (blast/shaft) smelting Cu. When burning risk of PAH production (need afterburner). In general, reduction in plastics concentration increase capacity shaft/blast Cu smelting furnace. Some unnecessary CO2 emisions?.

< 300.000 > 300.000 - no data

Phosphorus Contaminant (P2O5) SO2 gases sulphuric production.Risk to burn filters. Lost in slags. - - - no data

Halogenated FR and PVC Dioxines; Corrosive gases; metall losses no data no data - no dataPotassium Aggressive for furnace lining. Soluble slags with high level. < 20.000 - - no dataSelenium Toxic gases.Contaminant SO2 < 100 - >100 no dataSilver Colloidal form harmfull acuatic microorganism - - - -Sodium Aggressive for furnace lining. Soluble slags with high level. < 20.000 - - no dataTellurium Toxic gases.Contaminant SO2 < 100 - >100 no data

Tin Can be recovered with Pb as Sn/Pb alloy. Not always, not all Cu smelters. Risk of metal losses. < 300.000 - - no data

Tungten - < 100 no data - no dataZink Zink is recovered in Cu smelters as Zn oxide < 100.000 no data - no data

Metallic coatings on plastics Costly recycling. Metal air emission when burning - - - no dataOrganic coatings on plastics Not good for material recycling; energy recovery obligatory. - - - -

Substance/Element

Impurities content. Threshold limits on Cu smelters: (ppm)

Problems and Risk on Cu smelters.



3.4 ConclusionsAfter all the tests carried out, there are some conclusions about the results in the mechanical treatment line.

From the technical point of view, mechanical treatment is a good solution for the studied EES components. It is not only possible to treat it but also to get valuable fractions with a high ad-ded value.

On one hand it is possible to get concentrated fractions that can be introduced in advanced steps in the metallurgical processes. On the other hand it is possible to recover the plastic fraction separately. Without presence of metals it can be used in cement plants as coque substitute, and for energy recovery.

Within this SEES project is also studied the possibility of separating and recycling the plastic fraction. This would be a great advantage in the process, since the plastic fraction means an important percentage of the weight, specially in some of the components and fractions stud-ied.

About motors and alternators there is not a clear solution from the technical point of view in a secondary mechanical treatment plant.

The material is not very convenient for the shredders. Furthermore, there are lot of problems in the separation of copper coils and magnetic iron cores which means the major source of copper contamination in steel fraction. The same is happening in car shredders.

The proposal in principle would be to send this fraction to metallurgical process directly.

4 Chemical Recycling

4.1 Identification of Technologies for Chemical RecyclingThis section of the report details chemical based and related approaches that have been de-veloped for materials recovery from electronic scrap and discusses technologies that may be suitable for the integration of a chemical recycling methodology within an overall approach to materials recovery that aims to capture the most value from both the metallic and non-metal-lic fractions found in vehicle electronic scrap. A key requirement for the technical and eco-nomic success of any chemical recycling route will be the ability to source a suitable feed-stock that is rich in the materials to be recovered and which consumes a minimum amount of chemicals during the recovery process. An efficient method will ideally also offer good mater-ial recovery selectivity in order to enhance the overall efficiency of the process.

The success of chemical recycling from a commercial perspective will thus depend on its ability to integrate with complimentary mechanical separation and comminution techniques applied at earlier stages of the recycling process so that a suitable feedstock can be sup-plied.

In order to optimise the efficiency of any chemical recycling route for automotive electronic scrap it is vital that the scrap to be treated is separated from the overall vehicle scrap. The electronics in automotive scrap comes from a variety of sources within the vehicle such as engine management systems, in-car entertainment units, air bag actuators, satellite naviga-tion systems and a whole range of electromechanical controls for electric windows, seat ad-



justments, climate control etc as well as many other applications. Each of these is located in a specific position throughout the car and requires significantly varying levels of dismantling to be undertaken if they are to be segregated from the vehicle before any mechanical frag-mentation and subsequent recycling. One of the first challenges, therefore, in determining the effectiveness of a chemical recycling approach for end-of-life electronics scrap will be to de-termine the value of the recoverable materials in each particular electronic component type found within a car and to determine whether there is sufficient value to cover not only the costs of recycling but also the costs associated with getting the electronics to a stage where chemical recovery can be implemented. In most cases, in order to be viable, chemical recyc-ling is likely to be applied to populated printed circuit boards that have been removed from their accompanying casings and which have been ground to a relatively small particle size. This means that a significant degree of dismantling and segregation of the electronics will be required before chemical recycling can be employed. Without this effective concentration of valuable materials, the chemical recycling process is likely to require excessive volumes of chemicals to be used simply for dissolving additional materials, such as base metals, that are of relatively low value or which could be better recovered using mechanical separation meth-ods. In terms of a whole, end-of-life vehicle, it is possible to envisage a degree of manual dis-mantling, whereby electronic modules of value are removed from the vehicle before it is sub-jected to any mechanical shredding and comminution stages.

Alternatively, it may be possible to employ a wholly automated mechanical process prior to separate metallic and non-metallic fractions and also to segregate magnetic from nonmag-netic fractions, but it seems unlikely that this latter approach will be able to produce a suffi-ciently concentrated form of electronic scrap that would make chemical recycling worthwhile.

Assuming that the principal application for chemical recycling will be in the treatment of elec-tronic modules such as populated circuit boards, i.e. boards containing a range of active and passive components, as well as materials from numerous other related parts such as relays, connectors, transformers, heat sinks and coils etc, it will be necessary to understand where materials of value are likely to be found and in what concentrations.

4.1.1 Recycling of Electronic Assemblies using Chemical Recovery methods

Printed Circuit Boards (PCBs) are typically made from reinforced polymeric materials and range in cost and quality from the low cost paper filled phenolic materials found in consumer electronics through the glass fibre reinforced epoxide based laminates, to more expensive higher performance materials which use high temperature resistant, chemically and thermally stable polymers such as polyimides and PTFE. In automotive electronics applications, there will be a range of materials encountered; in-car entertainment systems are likely to employ low cost single sided paper filled phenolic type laminates, whilst those employed in under bonnet applications are likely to require more stable, higher performance materials. Although the polymer and reinforcement components of a PCB laminate are unlikely to contain materi-als that are of as much value as the precious metals they could still be recovered using chemical means such as solvolysis. Consequently, a good understanding of their chemical composition will be needed when embarking on the development of an integrated chemical recovery route. This is because the chemicals used for metal recovery and recycling are typ-ically strong acids and highly oxidising and may interact with the materials in the laminate.



In addition to conventional resins and glass fibres, there may also be, for example, a large quantity of bromine, that forms part of the flame retardant system of the laminate as well as remains of silane based coupling agents.

A typical PCB will have metallic conductors that are formed by the etching of patterns in a laminated copper foil structure. In the simplest PCBs the copper will be on only one surface of the board and it is thus known as a single-sided board. More sophisticated boards may be double-sided or even multi-layered. In this latter case several layers of copper may be sand-wiched inside the circuit board and thus for successful recovery of the copper etc, it will be necessary to have access to these layers. It is therefore important that end-of-life circuit boards are subjected to a suitable initial mechanical or possibly chemical process which will allow the chemicals used in the subsequent metal recovery process to reach the encapsu-lated copper inner layers. Depending on the board design, the copper could typically cover 25% of the circuit board area and would vary in thickness from less than 20 microns to more than 200 microns if the conductors need to carry a significant current. In double-sided and multi-layer boards it is necessary to provide interconnections between the various layers of copper and this is achieved by depositing copper in holes drilled in the boards. Because metal has to be deposited on the non-conducting dielectric layers in the hole, it is not initially possible to electroplate the copper and a so-called electroless copper deposition process is employed that uses an autocatalytic reaction to deposit copper from a solution. This depos-ition reaction is initiated using a palladium based catalyst, which is first deposited onto the dielectric in the holes and thus many scrap circuit boards may contain valuable quantities of palladium as well as the copper. In addition to the copper conductors on the board and any underlying palladium, a circuit board may also have a variety of other metals applied to it to impart a solderable finish on the surface of the copper. In many traditional circuit boards, the solderable finish applied to the copper is a so-called HASL (Hot Air Solder Levelled) finish which deposits a layer of tin-lead onto the copper. However, with the widespread adoption of surface mount technology and the move to much smaller components and interconnect structures, a number of more planar solderable finishes have been adopted and these can utilise a variety of metals including nickel, gold, silver, tin or even palladium. Thus, even be-fore any components are soldered to the board, there is a range of metals that may be en-countered in varying quantities and which could be recovered using chemical recycling tech-niques. A schematic representation of a section through a printed circuit board is shown in Figure 37 and this gives an indication of where the metals may typically be found.



Figure 37 A schematic representation of a section through a typical PCB

As manufactured, and before assembly with components, a typical printed circuit board may thus contain several metals that may be worth recovering and recycling. Almost without ex-ception the principle conductors will be formed from copper and may be found both on the surface of the boards but also, in the case of multi-layer boards, inside the multi-layer struc-ture and in the plated interconnection holes. In this latter case, there are also likely to be quantities of palladium that have been used to catalyse the initial deposition of copper in the holes. Finally, on the solderable surfaces of the board, there will be a solderable finish which may contain a variety of metals. The metals found in a bare circuit board are summarised in Table 4.

Table 4 Typical materials found in a bare circuit board i.e. before assembly.

Material Function LocationCopper Electrical conductor Board surface, inner layers and

plated holes

Palladium Catalyst for metal deposition Plated through holes and on solderable pads

Tin-lead, tin, silver, nickel, gold, palladium

Solderable finish, protecting copper from oxidation

Solderable areas on circuit board surface

Thermosetting resins e.g. epox-ides, phenolics and others

Dielectric to provide mechan-ical support of conductors and electrical insulation

Bulk of circuit board

Brominated resins To impart flame retardancy to board

Within the main body of the cir-cuit board

Glass fibres To reinforce the resin system and enhance the mechanical properties

Within the resin matrix of the circuit board

However, although there is a need to recover materials from bare circuit boards, the ones en-countered in end-of-life vehicles will be populated with components and thus contain a much



greater variety of both metallic and non-metallic materials which may make recycling and re-covery more difficult but possibly also more economically viable. Nevertheless, some work has been carried out on the recovery of metals found in bare PCBs as well as from the metal rich solutions generated during certain parts of the PCB manufacturing process. The tech-niques developed may be adaptable for use with populated boards and thus they are also in-troduced later in the review of chemical recycling techniques. Examples here include the electrochemical recovery of copper and more advanced methods for the recovery of copper, tin and lead from a single leachate solution.

In order to produce a functioning electronic device, the various components and other as-semblies are typically soldered on to the circuit board and it is at this stage that a number of additional metals will be added in the form of solder. Conventional solders used in electronics assembly are based on a tin-lead alloy and this is what is most likely to be encountered in electronics currently found in scrap vehicles. However, forthcoming European legislation (RoHS directive) will proscribe the use of lead in solders for most applications and this means that a number of lead-free alternatives are now being introduced. Interestingly, one of the preferred alternative lead-free solders is an alloy based on tin, silver and copper and, be-cause of the presence of an appreciable amount of silver (up to 4% by weight) in these for-mulations, the value of the solder is significantly increased. Recovery of these materials will thus become increasingly important as electronics assemblers change to lead-free solders. There are also a number of other lead-free alloys that may find increasing use and these can contain other metals such as antimony, bismuth and indium, which are not normally en-countered in mainstream electronics soldering applications.

Once the components have been assembled onto a circuit board, the mix of materials likely to be encountered becomes much wider and variable according to the specific application. There will be active and passive components as well as various other related devices such as switches, relays, connectors and heatsinks, in various proportions. Semiconductor devices will typically be silicon based and, in the case of plastic encapsulated devices, gold will often be present in the wire bonds that connect the silicon to the lead-frame. This will be encapsulated inside a thermosetting epoxy resin based material and some degree of com-minution or solvolysis will be required in order to facilitate access for chemical recovery. Gold may also be found in the contacts of relays, key pads and connectors.

Passive components may contain an even wider range of materials such as tantalum, lead, and aluminium in capacitors and various metal oxides in resistors. Elements such as gallium, indium, titanium, silicon, germanium, arsenic, antimony and tellurium may also be found in certain types of devices. Aluminium is found in significant quantities in both heat sinks and in aluminium capacitors and is thus likely to be found in any leachate solutions destined for metal recovery. Despite being amphoteric, aluminium cannot be recovered by electrolytic methods and thus is likely to add complications to any chemistry-based metal recovery and recycling processes. Serious attention will this need to be given to the separation and re-moval of aluminium from electronic scrap prior to the chemical treatment stages. Iron is also likely to be present in significant quantities, since it is found in leadframes, transformer cores and other metal parts used in electromechanical components. For example, the inside of a typical in car entertainment system such as a radio cassette player contains a large amount of electromechanical apparatus much of which is steel based and yet also intimately linked with the electronic functions.



4.1.2 The Material Characterisation of Printed Circuit Boards

The presence and quantity of each metal in a PCB will vary depending on the design, the specific application and the type of board function required. The board used in an in-car en-tertainment system will be significantly different from that used in an engine management system and the value of the metals in each is also likely to vary significantly. A key activity in the SEES project has therefore been to determine the levels of metals in each of the 14 dif -ferent categories of electronics that may be found in a typical modern vehicle.

By way of an example, the metal content of a solution that was formed by leaching all of the metals from a mixture of scrap printed circuit board is shown in Table 5 below.

Table 5 Metal content found in a leachate solution from a mix of scrap PCBs

Element Ag Au Cu Fe Pb Pd Sn

Concentration (mol/m3) 1.0 0.1 472 269 5.0 0.29 33.5

It is interesting to note that, although as expected, copper is the predominant metal, there was also a significant proportion of iron while most of the more valuable materials were present, not surprisingly, at relatively low concentrations. A second analysis of the metal con-tent of a different batch of mixed circuit board scrap was carried out and the data was used to determine the value of the scrap in terms of dollars per kilogramme based on the current market value of the metals This information is shown in Table 6 below. Based on the metal exchange prices as of 15th September 2004, the table shows the amounts of each metal found, its value per kilogramme of scrap and the total value of the metals per kilogramme of scrap. This initial data was again determined for a leachate solution from a mixture of board types and, at this stage, no attempt had been made to select boards known to have a larger quantity of metals and a higher value. The total value of the metal content in this example was found to be just under one US dollar per kilogramme of scrap and, whilst this probably represents a reasonable average figure for mixed scrap. Discussions with a board recycling company have indicated that by careful selection of board types it may be possible to double this figure to give a value of around two dollars per kilogramme.

Table 6 Value of metals found in leachate from mixed PCB scrap

Cu Sn Pb Pd Ag Au Ni

Conc. (ppm) 72870 1253 972 91 18 11 9

Price ($/kg) 2.82 9.09 0.93 6711 201 13015 13.04

Value ($/kg PCB) 0.20 0.01 0 0.61 0 0.14 0

One of the clear challenges for a chemical method is the recovery of all of the contained metals within a scrap assembly. When electronic scrap is subjected to the smelting route for the recovery of metals, all of the valuable materials may be accessed whereas, with the chemical route, the efficiency of the process will be determined by the access of the dissolu-tion chemistry to the materials of value. This efficiency will need to be determined for different



types of scrap by comparing, for example, the total metal assay for a unit with the quantities of metal recovered using a chemical method. Table 7 below gives further additional informa-tion on the composition of typical printed circuit board scrap and it makes an interesting com-parison with the data shown above.

Table 7 Composition of a scrap printed circuit board

Material Percentage (by weight)GRP (glass-reinforced polymer) >70

Copper 16

Solder 4

Iron, ferrite (from transformer cores etc ) 3

Nickel 2

Silver 0.05

Gold 0.01

Palladium 0.01

Other (bismuth, antimony, tantalum etc) <0.01

4.1.3 General Electronic Scrap Recycling Considerations

Electronic scrap has traditionally been subjected to recycling and recovery techniques only if an assay shows the presence of significant quantities of precious metals. In this case the ma-terials are sent to a metal smelter for recovery, whereas those deemed to have no recover-able value are sent to landfill. Specific figures relating specifically to the volumes of Printed Circuit Board (PCB) scrap produced are not readily available and perceived quantifications vary greatly. From discussions with key recycling industry personnel held in 2001 it appeared that ~50,000 tonnes per annum of PCB scrap was generated within the UK of which an es-timated 40,000 tonnes per annum comprises populated boards. The remaining 10,000 tonnes is either unpopulated boards or associated board manufacturing scrap, such as off-cuts etc.

Of this 50,000 tonnes per annum of estimated PCB scrap, it was further estimated that only ~15% was subject to any form of recycling with the remainder being consigned to landfill. Ap-proximately 60% of the estimated landfill demand of 42,500 tonnes per annum is believed to be consigned within the total redundant equipment package. A proportion of what would primarily be landfill demand was also met by off-shore shipments to China for disassembly and pyrolysis. Recycling in this current context is purely the recovery via smelting of the metal content. With the growing desire to move to a more sustainable approach to materials consumption and the need comply with electronics recycling legislation such as the WEEE Directive there is clearly an opportunity to develop new techniques such as the chemical re-cycling methods.



4.1.4 Details of Chemical Recycling Technologies

Chemical, i.e. hydrometallurgical, approaches to metal recovery from electronic scrap de-pend on the use of either selective or non-selective dissolution methods to achieve complete solubilisation of all the contained metallic fractions within a scrap electronic assembly. Whilst all hydrometallurgical approaches will be enhanced by the use of a prior mechanical commin-ution process, this is often primarily undertaken to reduce the bulk volume and to expose a greater surface area of the contained metals to the etching chemistry. In terms of the chem-ical approaches that can be used, these may either seek to dissolve all metals for recovery or they may use a selective dissolution whereby materials of value are individually dissolved in a more sequential approach. Selective dissolution approaches utilise a range of high capacity etching chemistries such as those based on cupric chloride or ammonium sulphate for cop-per removal, nitric acid based chemistries for solder (tin-lead) dissolution and aqua regia for precious metals dissolution. Non-selective dissolution may be carried out with either aqua re-gia or hydrochloric acid/chlorine based chemistry.

The dissolved metals generated via chemical dissolution from scrap electronics are present as ionised species within an aqueous media and many can be recovered by employing high efficiency electrolytic recovery systems. In the instance of selective dissolution, a single metal is recovered as pure electrolytic grade material, usually in sheet form, from the spent etching solution.

If the appropriate etching chemistries are chosen, it may also be possible to regenerate the li-quors for reuse as etchants. In the instance of selective dissolution, use may be made of the differing electropositivities of the ionised metallic species to enable the selective recovery of metals at discrete levels of applied voltage. Both approaches have advantages and disad-vantages depending on the type of electronic scrap being treated and these are discussed in further detail in the following sections.

4.1.5 Overview of Key Chemical Recovery Methods

In a review of printed circuit board recycling carried out by Goosey and Kellner in 2001 (1), it was found that a number of chemical i.e. hydrometallurgical approaches had been taken to the pilot plant stages of development. Preliminary cost studies indicated that the potential re-covery of all materials, with the exception of those from discrete components, could yield an operational profit of around $200 per tonne of electronic scrap treated.

On a relatively small scale, a number of hydrometallurgical approaches have been tradition-ally pursued specifically for the recovery of gold from pins and edge connectors found in electronic scrap. These methodologies have usually been deployed on discrete edge con-nectors and gold coated assemblies that have been manually separated from the scrap cir-cuit board via the use of air knives etc. The approaches have either liberated gold as metal flake via acidic dissolution of the copper substrates or dissolution of the gold in cyanide or thiourea based leachants followed by electrowinning or chemical displacement/precipitation with powdered zinc.

The use of non-selective leachants to dissolve the non-precious metal content of scrap PCBs has also received considerable attention. Various studies have been undertaken into the vi-ability of utilising dilute mineral acids in conjunction with subsequent metal recovery tech-



niques based on concentration and separation such as solvent extraction, ion exchange, ad-sorption and cementation.

In the UK, two potentially significant development projects have developed hydrometallur-gical approaches to the recycling of scrap PCBs with both having demonstrated viability to a pre-pilot plant stage. The first of these is that of Imperial College, London, which has taken shredded and classified sub-4mm populated PCB scrap through a single leachate route com-prising electro-generated chlorine in an acidic aqueous solution of high chloride ion activity. This has produced a multi-metal leach electrolyte containing all of the available metal content at generally mass transport controlled rates with respect to dissolved chlorine.

The viability of subsequent metal recovery via electrolytic membrane cells with discrete metal separation has also been demonstrated. The second of these approaches is from a Cam-bridge University led consortium and it employs a selective dissolution and electrolytic recov-ery route for discrete metal constituents. The solder recovery stage uses a solder selective (non-copper etching) regenerable leachant based on fluoroboric acid. This may or may not be deployed prior to mechanical pre-treatment, from which the dissolved solder can be elec-trolytically recovered in pure metallic form. Subsequent selective leaching of copper and pre-cious metals is then carried out. The ability to selectively remove solder prior to mechanical comminution has specific advantages in terms of enabling board disassembly whilst main-taining component integrity and recovery for possible testing and reuse.

Mechanical pre-treatment methodologies followed by the Cambridge Group have included shredding, magnetic separation, eddy current separation and classification. These two tech-niques are now described in more detail.

4.1.5.1 The Imperial College Methodology

Workers at Imperial College, London (2), have developed a novel aqueous leaching and electrowinning process for the recycling of metals such as gold, silver, copper, palladium, tin and lead etc from electronic and similar scrap. This technology is a good example of the route which uses non-selective initial dissolution of the metals in the scrap prior to selective electrochemical recovery. Using an electrochemical reactor, oxidant species are generated at a titanium/ruthenium oxide anode in an acidic aqueous chloride electrolyte and these are used in a leach reactor to drive the non-selective oxidative dissolution of metals from the electronic scrap. In order to enhance the efficiency of the process, the electronic scrap was first shredded to smaller than four millimetre sized particles. The dissolved metals are then recovered from solution by electrodeposition at a graphite felt cathode, as the counter reac-tion for the anodic generation of chlorine. Hence, the overall process involves inputting elec-trical energy to move the metals from scrap to cathode and, in principle, produces only a de-metallised waste. The presence of metals such as tin required electrolytes with hydrochloric acid concentrations of greater than 1 Molar in order to solubilise the metal and chloride activ-ities >1 are needed to increase silver and lead solubilities, and to minimise passivation of the leaching process.

A prime driver for this work was the fact that such a process would be a significant improve-ment on the currently operated pyrometallurgical processes, as it would maximise metal re-covery with low specific energy consumption and obviate the need for treating the noxious gaseous emissions from pyrometallurgical processes. The objective of the work undertaken



was to carry out a non-selective metal dissolution process, using anodically generated chlor-ine as oxidant, followed by metal recovery in an electrochemical reactor, with the option of selective recovery. This involved the use of highly concentrated HCl + NaCl electrolytes (ca. 5M Cl-, pH < 1) to increase the solubilities of various metals, with electrogenerated chlorine as the oxidant to drive a non-selective metal dissolution process. The overall process chem-istry involved is shown in the following reaction equations. In an electrochemical reactor, chlorine is generated at a titanium/ruthenium dioxide anode in acidic aqueous chloride elec-trolyte:

[1] 2Cl- -------> Cl2 + 2e-

This is then used in a leach reactor to drive the oxidative dissolution of those metals from electronic scrap:

[2] Mscrap + (n – z) Cl- + z/2 Cl2 -------> MCln(n-z)-

The metals are recovered from solution by electrodeposition as the counter reaction for the anodic generation of chlorine:

[3] MCln(n-z)- + ze- -------> Mwon + nCl-

Hence, the overall reaction in the electrochemical reactor is:

[4] MCln(n-z)- -------> Mwon + + (n – z)Cl- (catholyte) + z/2 Cl2

Thus, the overall process effectively involves inputting electrical energy to move the metals from the scrap to the cathode and produces only a de-metallised waste, the net chemical change being the sum of reactions [3] and [5]:

[5] Mscrap -------> Mwon

The primary loss in cathode current efficiency arises from dissolved chlorine being returned from the leach reactor and reduced at the catholyte, rather than on the metal scrap. An ion exchange membrane allowing chloride ion transport, but inhibiting transport of large anionic metal chloride complexes, must be incorporated in the reactor to enable recycling of chloride from catholyte to anolyte.

Selective electrolytic recovery of gold and palladium, silver, copper, and tin and lead under mass transport control was realised by the application of sequential applied varying depos-ition potentials.

A clear significance of this technology is that a single dissolution stage for all the metals con-tained within an input feed of shredded circuit board material can be effected within a con-trolled reaction environment. This obviates the interstage pollution and contamination prob-lems that may be inherent in a multi-stage dissolution process, albeit with perhaps a less effi-cient electrolytic recovery route.

Imperial College foresee the potential significance of this work and are currently working with a number of industrial partners to progress the project through to a dedicated pilot plant stage comprising a reactor system with the capability to process up to 100 kg per day of scrap board material and which will be utilised to address outstanding issues highlighted within the project development phase. A complete life cycle analysis will need to be under-taken on the electronic scrap treated using this technology to enable a full and detailed ap-



praisal of its viability. The technology is also being evaluated within the SEES project to treat various types of electronic scrap from end-of-life vehicles.

4.1.5.2 Details of the Cambridge University Methodology

Although one of the main drivers for this technology development (3) was the desire to re-cover and recycle solder contained within scrap PCBs, a logical extension of the work was its integration within a complete hydrometallurgical treatment methodology for scrap PCB as-semblies. The hydrometallurgical approach developed for the selective dissolution of solder, copper and precious metals was considered technically successful and plans for progression to a pilot plant development stage have been outlined. Preliminary estimates indicated the cost of a 10,000 tonnes per annum capacity treatment plant as being around $6M and that such would show an operational profit on metals recovered of $180 per tonne, with the value of recovered components being up to $3000 per tonne of material processed.

A specific advantage of the hydrometallurgical approach is the ability to process waste con-taining bismuth which has a persistence when present in smelter feedstock. Another specific advantage of this hydrometallurgical approach is the ability to initially desolder components from unshredded boards with the consequent opportunity for non-destructive disassembly and recycling. The process stages in this hydrometallurgical route are shown in Figure 38.

Figure 38 Process stages on the Cambridge University chemical recovery route

The method involves the selective dissolution of the solder connecting components to the cir-cuit board and tests undertaken have indicated no loss in functionality or performance of components recovered in such a manner. However, the value of this component recovery ap-proach is heavily dependent on the market price for specific recovered components.



Since only a minority of the components recovered form electronic scrap have a potential for reuse and recycling, it may be that more selective dismantling techniques such as the select-ive desoldering and removal methodology employed by SAT in Vienna offer more potential. Reductions in market potential for components recovered for reuse applications will mean that shredding of the boards prior to leaching can be undertaken to promotes both ease of handling. Shredding also permits the use of beneficial pre-treatment methods such as mag-netic and eddy current separation, prior to exposure to the chemistry and this enables a more concentrated feedstock to be treated with the concomitant reduction in quantities of chemic-als used. Eddy current separation and magnetic separation may be simultaneously deployed to effect a three-way separation of shredded particulate matter. A conveyor belt looping over a rapidly rotating permanent magnet enables a current to be induced within conductors in the shredded feedstock. The induced current tends to eddy around the randomly shaped particles creating a secondary magnetic field around them. Interaction of this field with the changing magnetic flux within the pulley head causes such particles to be ejected from the falling stream of granulated matter. This separation is particularly effective in removing alu-minium which is widely used in electronic components and assemblies and which is undesir-able in many chemical recovery methods. Ferrous conductors will experience a magnetic pull towards the belt which overrides the eddy current induction and so cling to the belt long enough to be separated from the main bulk of the falling feedstock.

A particular novel technology of this hydrometallurgical route lies in the leaching of the solder, which is accomplished with no uptake of copper via the use of chemistry based upon fluoroboric acid in the presence of the titanium (IV) ion. Solder may then be recovered elec-trolytically from this leachant, which may in turn be regenerated for closed loop operation by subsequently increasing its oxidation state.

The basic reaction chemistry involved in this approach is as follows;

Leaching

Pb + 2HBF4 + 2Ti4+ --------> Pb (BF4)2 + 2Ti3+ + 2H+

Sn + 2HBF4 + 2Ti4+ --------> Sn (BF4)2 + 2Ti3+ + 2H+

Electrodeposition

Pb (BF4)2 + H2O --------> Pb + 2HBF4 + 1/2O2

Sn (BF4)2 + H2O --------> Sn + 2HBF4 + 1/2O2

Leachant Regeneration

2H+ + 1/2O2 + 2Ti3+--------> 2Ti4+ + H2O

Copper extraction and recovery follows the well-established route of dissolution via am-monium or cupric based chemistry with subsequent electrolytic recovery which may be integ-rated into a closed loop etchant regeneration system. Following copper extraction, the residues containing precious metal content may be dissolved in a chlorine based leachant and electrolytically recovered or be subjected to mechanical upgrading prior to smelting.

4.1.5.3 Other Chemical Recovery Methods

As early as 1984, Kolodziej and Adamski (4) of the Technical University in Wroclaw, Poland, published a paper detailing a ferric chloride based hydrometallurgical process for the recov-



ery of silver from metallic electronic scrap. In this work the scrap consisted of components in the form of various sized plates made of brass, beryllium bronze and pure copper with mech-anically pressed in pure silver contacts. The methodology proposed was to find conditions that would enable the dissolution of all of the base metals of the components i.e. principally zinc and copper, whilst leaving the silver contacts physically in tact. This was largely achieved by using a ferric chloride solution operating at 80°C. At this temperature, and with the weight ratio of ferric iron to brass equal to 2.7, 97% extraction of copper and zinc from the brass was achieved after one hour. If the leaching process was carried out with a concentra-tion of ferric chloride and phase ratio chosen so that in the final stage of leaching the concen-tration ratio of ferric to ferrous ions was not less than unity. Under these conditions the silver was only slightly solubilized due to a surface passivation that was found to contain both silver chloride and silver oxide.

In the early 1990s the National Institute for Resources and Environment in Japan reported work they had undertaken to recover valuable metals from printed wiring board wastes using a hydrometallurgical approach (5). At this time the drivers for metal recycling from printed cir-cuit boards were largely economic rather than legislative and circuit boards were simply re-garded as another source of metals, especially precious metals, in a similar way to conven-tionally mined metal ores. However, the author did note that the levels of precious metals found in printed circuit boards were continuing to diminish and that they were of reducing value for the recovery valuable materials. He also correctly predicted that this reduced value might encourage the discarding of boards with the subsequent introduction of various heavy metals into the environment. It was with the need to conserve the environment that this ex-perimental work on the feasibility of recovering metals from printed circuit boards was con-ducted. Saito carried out leaching tests on crushed samples of PCBs using a range of leach-ing agents including hydrochloric acid, nitric acid, sulphuric acid, sodium hydroxide, am-monium hydroxide, ammonium carbonate and ammonium thiocyanate.

For each leachant the quantities of metals dissolved from a 200 mesh sized fraction after 2 hours at 50°C were determined over a range of concentrations. Depending on the leachant and the conditions, it was possible to produce leachant solutions with varying concentrations of metals including copper, lead, tin, zinc, nickel and iron. Gold could be dissolved with a thiocyanate solution if hydrogen peroxide was added as an oxidising agent and the dissolu-tion of silver could be enhanced by the addition of ferric ions. The leaching solutions were then subjected to concentration and separation procedures such as solvent extraction, ion exchange and cementation to separate and recover the valuable materials.

An interesting approach to recovering copper form scrap printed circuit boards was described by Chien, Y., and Wang P. H., of the National Cheng Kung University in Taiwan. In a paper published in 2000 (6), a PCB recycling method was described which utilised the liquefaction of printed circuit board wastes in motor oil. The process was investigated to enable an evalu-ation of the feasibility of converting scrap materials from the printed circuit board manufactur-ing process into oils whilst also enabling copper recovery. The resins that comprise a major part of a printed circuit board laminate, are typically originally produced from crude oil and it has been shown that they can be thermally cracked into fuels or chemicals using appropriate conditions. These resins also represent a significant quantity of energy in terms of the energy consumed in processing petroleum. Thus recovery of this energy in a form with the highest possible value i.e. as fuel oil, is increasingly important.



Organic macromolecules i.e. the highly crosslinked resins in a printed circuit board laminate, are only soluble in heavy oils if they are cracked effectively and this starts to occur above 500º K when carbon-carbon bonds begin to be disrupted. In this work, liquefacation experi-ments were carried out over a range of temperatures form 513º to 673ºK. For example, when circuit boards were liquefied in motor oil at 593º K for 30 minutes these conditions generated 73% oils, 4% gases, and 23% copper rich residues. The oils produced from the liquefacation of the PCBs was found to be primarily naphtha and gas oil that could be refined for produc-tion of gasoline and diesel fuel. Over 90% of the copper from the liquefacation residue was recovered.

In addition to the processes developed by Imperial College and Cambridge University de-scribed above, there has been a considerable amount of other work carried out over the last ten years or so to develop other selective chemical methods for the recovery of valuable metals from waste printed circuit boards. Initially, much of this work focussed on the recovery of valuable materials from scrap and waste generated during the PCB manufacturing process rather than from end-of-life electronics. However, with the increasing focus on the need to re-cycle more end-of-life electronics and for a more sustainable approach to materials con-sumption, some of the earlier developed technologies are as equally applicable to end-of-life electronics as printed circuit board manufacturing scrap and process waste.

A good example of this dual applicability can be found with the chemical routes developed for the chemical recovery of tin, lead and copper. Initial work carried out during the 1990’s to re-cover these materials often focused on the recovery of tin, lead and, to a lesser extent cop-per, from etchants used in the PCB manufacturing process. In particular, it was widespread practice to use electroplated tin-lead etch resists in the outer layer patter forming process during printed circuit board fabrication. Once they had fulfilled their function, these materials were then removed to expose the underlying copper, using highly acidic stripping chemistries. The use of this type of process lead to the generation of large quantities of strongly acidic waste containing high concentrations of lead, tin and copper, which required expensive treatment and subsequent consignment to landfill. In the UK during the 1990s, the tin-lead stripping process was identified by a PCB industry environmental working group as being a key source of waste and inefficiency within the industry and something that needed a new approach in terms of metals recovery, recycling and waste minimisation.

Consequently, four organisations undertook a project with UK DTI funding to develop a novel process for the recovery of metals from spent etch resists. The patented technology de-veloped, which is outlined below, could also be used for the recovery of the same metals from end-of-life electronics i.e. for recovering metals from solder.

Tin-lead solder compositions are used extensively as etch resists during the manufacture of printed circuit boards and the subsequent necessity for their removal demands the applica-tion of suitably formulated stripping chemistry. Whilst there are a number of chemistries that can be used, essential process economics have lead to an almost universal usage of generic nitric acid based solutions. These are formulated to have high tin-lead removal rates and ca-pacities and are, moreover, generally proprietary compositions incorporating specific addi-tional active chemistries. These include ferric nitrate, to enable the chemical dissolution of the tin-copper intermetallic interface and chloride ions to maintain the dissolved tin in solution and complexant chemistry to minimise chemical attack on the underlying copper substrate.



These strippers have a finite capacity and are generally exhausted when they contain around 130 g/litre of solder. There is a subsequent requirement to treat and / or dispose of this spent chemistry. This not only represents an increasing cost for board manufacturers but is in-creasingly environmentally unacceptable. One of the most effective and environmentally be-neficial approaches to the treatment of heavy metal bearing solutions is one which recovers the metals in a pure metallic state. With many solutions containing heavy metals, electrolytic removal is an established and extensively applied technique. In the instance of spent tin-lead strippers, treatment equipment maximising the application of recovery technology has been developed. This was achieved by integrating physical separation, electrowinning and mem-brane technology into a dedicated piece of equipment. In the equipment developed by the group of organisations above, both lead and copper were recovered in pure metallic from dis-tinctly separate operations via electrolysis utilising cation exchange membranes. Tin was re-covered as the oxide using advanced filtration or other physical separation techniques.

Whilst the treatment of spent strippers was conducted on-line, it was accomplished by a batch methodology in which spent stripper was continuously discharged into an integrated storage vessel whilst the previous batch of spent etchant was being subjected to treatment.

The spent stripper was subjected to filtration prior to storage and continuous filtration during the final electrolytic stages was employed to remove stannic oxide. Both copper and lead were recovered electrolytically by employing spent stripper containing these metals as the anolyte within a membrane divided cells. Although both copper and lead could be recovered from the same cell, this occurred sequentially with the copper being extracted before lead re-covery commenced. To improve the efficiency of the electrolytic recovery, the treatment equipment included two distinct membrane cells, with one sited within the receipt storage vessel and being dedicated to copper recovery. This enabled a more effective batch treat-ment to be realized, as the spent stripper being held prior to the final lead recovery operation could be decoppered prior to transfer. A schematic diagram of the process equipment de-veloped in this project is shown in Figure 39.

Although this type of approach has been successfully demonstrated for spent etch resists containing metals originating from the PCB outer layer patterning process, the PCB industry has largely changed over to the use of pure tin based resists and this has effectively obviated the need for this type of equipment. However, if similar acid based stripping solutions were used to remove tin, lead and copper from end-of-life electronics, this type of equipment could provide a useful component of an integrated metal recovery strategy. With careful optimisa-tion of the stripping chemistries employed via the use of copper corrosion inhibitors, it might even be possible to use this type of approach to remove solder so that components could be recovered for reuse.

Work was also carried out by Scott et al. (7) at Newcastle University in the 1990 to investig-ate the electrochemical recycling of tin, lead and copper from stripping solutions used in the PCB manufacturing process. In this study a simple solution of aqueous nitric acid was used in place of the standard commercially available stripping solutions and two recycling method-ologies were studied. These were the electrochemical recycling of all metals and the combin-ation of electrochemical deposition of copper and the precipitation of tin and lead. In the latter approach the tin and lead could be recovered using furnace based recycling techniques. An interesting finding of this work was that pure nitric acid was more preferable from a recycling



perspective than the use of commercially available proprietary strippers because the ab-sence of additives such as corrosion inhibitors helped to facilitate metal recovery.

Figure 39 Schematic diagram of the module developed for recovery of tin, lead and copper from highly acidic metal bearing solutions.

As in the previous example, the removed tin formed a hydrated oxide, which was removed by filtration. In this case the oxide was then quickly redissolved in hydrochloric acid at 90°C (10% HCl, 15 minutes) and recovered by electrodeposition with between 70 and 85% effi -ciency depending on the tin concentration. Once the tin oxide had been filtered from the strip-ping solution, copper was then electrodeposited onto stainless steel cathodes with very high current efficiency. The copper deposits were of high purity, containing little or no tin and lead. Finally, when the copper had been removed, the lead was electrodeposited giving a powdery deposit that tended to fall off of the cathode and which redissolved unless the concentration of the nitric acid was reduced to levels where it would be too dilute to consider reusing it as a stripper. An alternative process examined utilised the precipitation of lead as the sulphate be-fore electrodeposition of the copper. The tin and lead could be precipitated from solution either together or sequentially depending on the subsequent recovery path chosen. For ex-ample, metal refiners can accept mixtures of stannic oxide and lead-sulphate for the produc-tion of tin-lead alloys. Although this method was described as being simple and economical, the authors acknowledged that it was not as environmentally friendly as total electrochemical recovery because metal refineries would eventually discharge further furnace gas and slag.

In a more recent publication from the same University, Mecucci and Scott (8) describe further work related to the above, to leach and electrochemically recover copper, tin and lead from scrap printed circuit boards. In this approach, nitric acid was again used to demonstrate the potential for the selective dissolution of copper and lead-from the boards. The nitric acid con-centration range used was from 1 to 6 mol/dm3 and precipitation of tin as the hydrated oxide



(metastannic acid) occurred at acid concentrations above 4 mol/dm3. As in the previous work, cathodic lead deposition resulted in dendritic metal formation, with subsequent re-dissolution and an overall poor current efficiency. Consequently, an alternative recovery method was de-veloped which employed electrodeposition of the copper at the cathode and lead dioxide de-position at the anode. Electrohydrolysis for acid and base regeneration from the spent nitric acid was also investigated. It was also found that, prior to metal leaching from the scrap boards, crushing or shredding was essential, in order to enhance the dissolution efficiency, especially with multilayer circuit boards where much of the copper is effectively buried inside the board.

Solvolysis is a chemical technique that can be used to provide better access to the metallic fractions contained both within printed circuit board and the components etc as well as en-abling the recovery of valuable organic fractions and glass fibres. This is because the major-ity of polymers used in electronic applications are thermosetting materials such as epoxide resins with high crosslink densities and good thermal and chemical stabilities developed spe-cifically to be stable and to provide protection of delicate electronic components. Whilst these properties are desirable in service they cause problems at end-of-life when metal recovery is being undertaken because they effectively encapsulate and protect the metals form chemical attack. As they are largely insoluble in conventional solvents, solvolysis provides and altern-ative approach to their removal and possible use in new applications. Solvolysis unlike con-ventional dissolution, involves reaction of the material with the solvent, such that one or more chemical bonds are ruptured so that the material actually reacts with the solvent in which it is ultimately dissolved.

Although, some work has been reported on the use of solvolysis in the recycling of electronic scrap, more work has been published on the solvolysis of thermosetting resins such as epox-ides. Although this work was not specifically aimed at the treatment of circuit board resins, the fact that many PCBs are made of epoxide based materials means that they may have ap-plicability in this type of application. El Gersifi et al (9) and (10) have, for example, published work on the solvolysis of epoxy-glass fibre composite materials. Glycolysis of anhydride hardened epoxy was relatively straight forward using tetrabutylorthosilicate as a catalyst. The depolymerisation was carried out almost to monomers and the glycolysis product comprised ester-diols, tetrols, and a glycol excess. The solvent excess could be eliminated by distillation under vacuum without producing products of higher molecular weight. Glycolysis of compos-ite materials was also found to be as efficient. The glass fibres were freed by de-aggregation of the epoxy matrix. The treatment of samples of large size yielded long fibres after solid-li -quid separation. After washing and drying, the level of organic contamination was below 0.05%. Similar work was reported by Terada et al on the solvolysis of epoxy resins used in composite magnet structures to enable the active components to be recovered. A new solvent-decomposition method was detailed which enables an epoxy resin to be easily de-composed. The process was used as a recycling and recovery method for the separation and recovery of magnetic powder from bonded magnets. Using this method, the polymer matrix can be chemically decomposed without degrading the embedded metallic materials and with minimal loss of quality. It was found that this process could be widely used for recycling com-posite materials containing various metals and composite materials and it could thus provide a specific element of an integrated recycling approach.



In the United States, a methodology based on solvolysis has been developed that enables both the more efficient recovery of metals and the recovery of polymeric materials with high quality. The process also offers the additional benefit of having the capability to extract both halogens and brominated hydrocarbon derivatives. Dumler-Gradl (11) et al reported work on the solvolysis of flame retarded circuit boards in which a method of removing brominated epoxy resins by solvolysis from flame retarded electronics scrap was described. Pieces of circuit board, chopped to less than 0.5 mm were suspend in solvents and autoclaved at 260-320ºC for between one and twelve hours at 50 to 110 bar of nitrogen and then filtered. Eth-anol was reported to give the most effective polymer degradation.

Related work has been reported by Jallot (12) in the PhD thesis ADEME, where treatment of scrap circuit boards was achieved using an initial chemical depolymerisation process. The work involved a systematic study of the influence of numerous parameters on the solvolysis performance for different PCBs. Only glycol based solvents associated with the basic core-agents used to make the PCB polymers were found suitable for making the entire polymer pass into solution for all PCBs studied. With the removal of the polymer, the process de-veloped allowed the recovery of glass fibres and metals with low levels of organic contamina-tion. The recovered glass fibres could be reused for further applications and the metals can be recovered electrochemically after dissolution. It was also found that the organic liquid, which contains large amounts of solvent, could be used for the solvolysis of PET waste in or-der to produce a precursor polyol for polyurethane foams with flame retardant properties ow-ing to the organobromine functionality in the polymer. Optimisation work was also carried out and process reproducibility and efficiency on a industrial sample of PCBs from PC waste were evaluated.

Oh and Lee from the Korea Chemical Company, in collaboration with Yang et al from the Chonnam National University in Korea, recently reported details of their work (13) on the se-lective leaching of valuable metals form waste printed circuit boards. This study was carried out on assembled circuit boards that had been obtained from scrap computers. One of the more interesting parts of this work was the level of mechanical comminution and segregation that was applied before the chemical leaching was started. After the boards had been re-moved from the computers, the first stage involved crushing with a shredder to particles that were no more than 1 mm in size. This particles were then passed through and electrostatic separator to give 30% conducting and 70% non-conducting fractions. The conducting frac-tion, which contained the metals was then subjected to magnetic separation where 42% was found to be magnetic and 58% non-magnetic. This series of separation steps effectively helped to concentrate the valuable metal fraction and it was the final nonmagnetic fraction that was subjected to chemical leaching. The main leachant solution was a solution of 2 M sulphuric acid and 0.2 M hydrogen peroxide which was used at 85°C. Treatment of the non-magnetic fraction in this solution for 12 hours gave a greater than 95% extraction of copper, iron, zinc, nickel and aluminium. The gold and silver were extracted at 40°C using a mixed solution containing ammonium thiosulphate, copper sulphate and ammonium hydroxide. After 24 hours in this solution all of the silver had been extracted and after 48 hours 95% of the gold had also been extracted. The residues were than reacted with a solution of sodium chloride for 2 hours at room temperature to extract the lead and finally, palladium was extrac-ted at room temperature using aqua regia. Most of the palladium was leached by 50% aqua regia within 3 hours using 10 grammes of solid residue per litre of etchant.



Workers at Osaka University have developed a new process for the dissolution of gold from printed circuit boards using a bioleaching process and this was presented at the recent Elec-tronics Goes Green Conference held in Berlin (14). The process used the bacterium Chro-mobacterium Violaceum to recover the gold from circuit boards having a gold plated thick-ness of around 70 nm, as would be typically found on an immersion gold solderable finish. Under the appropriate conditions these bacteria can both generate and destroy cyanide. Ini-tially, the cyanide generated is used to bring the gold from the PCB into solution and at a later stage the cyanide is converted to ethanoic acid. The thin gold coating was slowly dis-solved over 480 hours, so the use of such a process would obviously introduce a significant rate determining step in any integrated recycling approach. Work was carried out to optimise the conditions used in this process and it was found over the range of cyanide concentrations typically encountered there was little influence on the gold dissolution rate.

However, the oxygen levels in the solution did have an influence on the process and increas-ing the oxygen concentration was found to increase the gold dissolution rate. Under suitable conditions both copper and nickel could also be dissolved form circuit boards but work car-ried out on gold powder demonstrated the effectiveness of having a large surface area for the bacteria to attack. This again highlights the need for an efficient comminution process if these types of techniques are to operate within an integrated recovery scheme.

In January 2004, Li et al published a state of the art survey of printed circuit board recycling (15). Although it doesn’t give details of chemical recovery routes, this paper is particularly useful in that it reviews the literature from 1990 to the present day and reviews all aspects of the overall PCB recycling from end-of-life to the final mechanical and chemical recycling op-tions. The paper shows a typical recycling scheme that incorporates varies elements of dis-assembly, testing, pyrolysis and separation prior to mechanical and chemical processing. Po-tapov (16) has also produced a review of the recent patents and scientific and technical liter-ature on chemical methods for recycling valuable metals from scrap electronic and related devices. The review reports that chemical leaching procedures are suitable for the recovery of precious metals from this type of scrap, but no further analysis of the paper has been made as it is written in Russian.

4.1.6 Summary and Conclusions for Chemical Recovery Methods

The value of the electronics used in automotive applications is continually growing and rep-resents an increasing proportion of the total value of a car. Similarly, at end-of-life, the elec-tronics in a vehicle contains a significant quantity of materials that have value and which need to be recovered and recycled. Whilst the treatment of end-of-life vehicles has tradition-ally been via mechanical routes, there are number of chemical recovery methods that have potential for recovering the wide range of metals such as tin, lead, nickel, silver, palladium and gold, that are employed in vehicle electronics. Many of these chemical methods have been developed to address specific metals recovery requirements such as gold from con-nectors or tin and lead from solder, and their efficiency may be compromised if they are used in more non-specific metal recovery applications. Nevertheless, there are sufficient tech-niques available to encourage their further study as one key element of an overall integrated methodology for recovering as much value as possible from end-of-life electronics. The tech-nical viability of these methods has been demonstrated but the key determinant in their adop-tion will be their efficiency i.e. overall operating costs. Chemical recycling methods tend to be



specific for certain groups of metals and there is usually a need to upgrade scrap prior to chemical treatment in order to avoid unnecessary use of process chemistry. As a con-sequence, the success of any chemical recycling method will only be assured if it can be in-tegrated effectively with prior mechanical separation, comminution and segregation tech-niques. There will thus be a balance between the level and cost of upgrading the scrap prior to treatment with the increased efficiencies that this will bring to the chemical method. This balance will vary with the type of electronic scrap being processed and thus the more de-tailed analysis of each type of electronic product found in a vehicle will help to address this issue.

It seems clear, however, that with the increasing levels of environmental legislation and the general desire to recover, reuse and recycle materials, new electronic scrap waste treatment and recovery methodologies will become increasingly important. Chemical recovery meth-ods, if properly developed for specific applications, and if integrated within a broader overall recycling process, will provide at least one route for the recovery of valuable materials.

4.2 Chemical Recycling Study on selected Components

4.2.1 Comminution of PCB samples for chemical recycling

For any chemical recovery method the first stage required is a preliminary mechanical com-minution phase. This section addresses the size reduction processes that were applied to a selection of junction boxes supplied by LEAR. The types and quantities of the boards treated by GAIKER are shown in Table 8.

Table 8 Groups and amounts of PCB samples received from LEAR

Group Description Weight/kgPCB #1 Lead-free samples (PCBs from smart and passive JBs) 4.63

PCB #2 Electronic modules (Pb-free PCBs) 3.74

PCB #3 Smart JB passenger (Pb containing PCBs) 7.00

PCB #4 Electronic modules (SnPb PCBs) 3.60

PCB #5 Passive junction boxes (PCBs) 6.10

The initial stage of the treatment scheme was size reduction that combined impact and blade shredders. This treatment gave a mixture of sizes and materials, nominally over and under 12 mm.



Figure 40 PCB samples before and after first stage mechanical treatment

Large metallic pieces were detected in PCB#05 (shown in Figure 41). These were removed before the sample was introduced into the hammer mill due to concerns that the machine may be damaged during processing.



Figure 41 : Metallic screws removed before shredding sample PCB#05

Following on from the shredding process the boards were further size reduced by passing them through a hammer mill twice. These treatments produced a 10 mm size fraction and then a 5 mm fraction.

Figure 42 Hammer mill



Figure 43 PCB samples after second stage mechanical treatment

Some metallic materials such as big screws, copper wire and pieces of plastic (polyolefin) were removed from the process.



Figure 44 Undesirable fractions removed: copper wire, plastic, and screws

After the shredding process each PCB sample was sieved to produce the following size frac-tions: less than 1mm, 1 to 2mm, 2 to 4mm and greater than 4mm.

4.2.2 Results and discussion

A detailed break down of the material losses resulting from the shredding and hammer mill processes is provided in Appendix 1. It was observed that the material losses for PCB 2 and PCB 3 samples were much higher than for the other PCB samples. This may be explained in the way these samples were treated, as they were shredded straight away from the shredder to 5 mm size. However, this is not the correct approach since it is very important to shred gradually so as not to obstruct the hammer mill and to keep all the material.

Additionally, it was noted that PCB 3 was very tough because there was a lower glass fibre content. Consequently, there were higher material losses such as copper wire, metallic and plastic pieces.

4.2.3 Populated PCB characterisation study

In order to determine the value of PCB related scrap from EES, a detailed analysis has been undertaken to identify the metals content of various ground PCB fractions. The EES from end-of-life vehicles has been divided into 14 distinct categories (see SEES D1 Report) and each of these will have varying quantities of valuable materials. Also, as any chemical recov-ery method will follow on from a previous mechanical comminution phase, there is likely to be an optimum particle size that offers the most efficiency from a chemical recycling perspect-ive. It was reasonable to expect that the smaller the particle size that can be produced mech-anically, the easier it will be to extract valuable metals. However, the additional mechanical input required to produce the smaller size may negate any additional value recovered due to its own inherent costs. Part of this characterisation study was aimed at determining the op-timum particle size for metal extraction prior to chemical recovery. The additional purpose was to grade the various PCB samples in terms of valuable metal content.

Methodology

Five PCB samples were provided by LEAR (PCB 1, 2, 3, 4 and 5) as shown in Table 8 and these were ground by GAIKER as described in the previous section into four different size fractions;

Greater than 4mm

Between 4mm and 2mm



Bewteen 2mm and 1mm

Less than 1mm

Each sample (50 g) was placed into a beaker (1 dm3) and Aqua Regia (500 cm3) was added. The solutions were stirred for 24 hours. Aliquots (2 cm3) were taken from each solution after 2, 4, 6 and 24 hours and each sample was diluted to 250 cm3 in a volumetric flask (500 cm3). The resulting solutions were then analyzed using inductively coupled plasma-optical emis-sion spectroscopy (ICP-OES) to determine the concentrations of each metal present (Au, Pd, Cu, Ni, Pb, Fe, Ag, Al and Sn). The instrument used was a Perkin Elmer 4300DV ICP-OES and the method used was an adaptation of the UKAS accredited method for detecting metals in soils.

Results

See Table 9 and Table 10 for reference data showing total metal contents and metal values.

PCB 1 – Smart and passive junction boxes, Lead-free

<1mm size fraction – The total metal content was determined to be 315 kg per tonne of PCB. This represented a total metal value of €1240. Table 2a in Appendix 2 shows the percentage metal contents and values for the individual metals stated. Copper was found to be present in the highest content followed by Iron and Tin. Copper also presents the highest value metal. However, despite their low contents gold, palladium and nickel presented high values due to their higher market values compared to aluminium, iron and lead. Tin also presented high value for content.

1 to 2mm Size fraction - The total metal content was determined to be 674 kg per tonne of PCB. This represented a total metal value of €3227. Table 2b in Appendix 2 shows the per-centage metal contents and values for the individual metals stated. The retrievable metal val-ues are calculated based on their current market values. Copper was present in the highest content followed by tin and iron. Copper also presented the highest value metal. Again, des-pite their low contents gold and palladium presented high value due to their higher market values compared to aluminium, iron and lead. Tin again presented high value for content. The overall metal content and value for the 1 to 2mm size fraction had increased significantly compared to the <1mm size fraction.

2 to 4mm Size fraction - The total metal content was determined to be 968 kg per tonne of PCB. This represented a total metal value of €3689. Table 2c in Appendix 2 shows the per-centage metal contents and values for the individual metals stated. Copper was present in highest content followed by iron and tin. Copper also presented the highest value metal. Again, despite their low contents gold and palladium presented high value due to their higher market values compared to aluminium, iron and lead. Tin again presented high value for con-tent. The overall metal content and value for the 2 to 4mm size fraction had increased signi-ficantly compared to <1mm and 1 to 2mm size fractions.

>4mm Size fraction - The total metal content was determined to be 890 kg per tonne of PCB. This represented a total metal value of €2981. Table 2d in Appendix 2 shows the percentage metal contents and values for this size fraction. Copper was present in highest content fol-lowed by iron and tin. Copper presented the highest value metal. Again, despite their low contents gold and palladium presented high value compared to aluminium, iron and lead. Tin again presented high value for content. The overall metal content and value for the >4mm



size fraction had decreased compared to the 2 to 4mm size fraction. The 2 to 4mm size frac-tion presented the highest metal content and value.

PCB 2 – Electronic module, lead-free

<1 mm size fraction – the total metal content was determined to be 399 kg per tonne of PCB. This represented a total metal value of €2972. See Table 3a in Appendix 2 for a breakdown of individual metal percentage content and value. Copper was present in highest content fol-lowed by tin and iron. Copper also presented the highest value metal. However, despite their low contents, gold, palladium and nickel presented high value compared to aluminium, iron and lead. Tin also presented high value for content.

1 to 2 mm size fraction - the total metal content was determined to be 654 kg per tonne of PCB. This represented a total metal value of €3314. See Table 3b in Appendix 2 for percent-age metal contents and values. Copper was present in highest content followed by tin and lead. Copper also presented the highest value metal. Gold and palladium and nickel presen-ted high value. Tin presented high value for content. The overall metal content and value for the 1 to 2 mm size fraction had increased compared to the <1 mm size fraction.

2 to 4 mm size fraction - the total metal content was 591 kg per tonne of PCB at a value of €2909. See Table 3c in Appendix 2 for individual metal contents and values expressed as a percentage of totals. Copper was present in highest content followed by aluminium, iron and tin. Copper also presented the highest value metal. Gold and palladium presented high value. Tin again presented high value for content. Aluminium was present in high concentra-tion and moderate value. The overall metal content and value for the 2 to 4 mm size fraction had decreased compared to the <1 mm and 1 to 2 mm size fractions.

>4 mm size fraction - the total metal content was 462 kg per Tonne of PCB at a value of €2596. See Table 3d in Appendix 2 for metal content and values. Copper was present in highest content followed by iron and aluminium. Copper presented the highest value metal. Gold and palladium presented high value. Aluminium was present in high concentration and moderate value. The overall metal content and value for the >4 mm size fraction had de-creased compared to the 2 to 4 mm size fraction. The 1 to 2 mm size fraction presented the highest metal content and value.

PCB 3 – Smart junction boxes, lead-tin solder

<1 mm size fraction – the total metal content was determined to be 385 kg per tonne of PCB at a total metal value of €1924. See Table 4a in Appendix 2 for metal contents and values. Copper was present in highest content followed by tin, lead and iron. copper also presented the highest value metal. Gold, palladium, tin and nickel presented high value compared to aluminium, iron and lead.

1 to 2 mm size fraction - the total metal content was 790 kg per tonne of PCB. This represen-ted a total metal value of €3710. See Table 4b in Appendix 2. Copper was present in highest content followed by tin and lead. Copper also presents the highest value metal. Gold, palla-dium and tin presented high value. The overall metal content and value for the 1 to 2 mm size fraction had increased significantly compared to the <1mm size fraction.

2 to 4 mm size fraction - the total metal content was 969 kg per Tonne of PCB. This repres-ented a total metal value of €3582. See Table 4c in Appendix 2. Copper was present in highest content followed by iron and tin. Copper also presented the highest value metal. Pal-



ladium presented a high value compared aluminium, iron and lead. Tin again presented high value for content. There was no sufficiently measurable quantity of gold present. The overall metal content and value for the 2 to 4 mm size fraction had decreased compared to the 1 to 2 mm size fraction.

>4 mm size fraction - the total metal content was 1063 kg per tonne of PCB at a total metal value of €2278. See Table 4d in Appendix 2. Copper was present in highest content followed by iron. Copper presented the highest value metal. Other metals were in small quantities and did not represent significant value. The overall metal content and value for the >4 mm size fraction had decreased compared to the 2 to 4 mm size fraction. The 1 to 2 mm size fraction presented the highest metal content and value.

PCB 4 – Electronic modules, lead-tin solder

<1 mm size fraction – the total metal content was determined to be 356 kg per tonne of PCB at a total metal value of €2050. See Table 5a in Appendix 2 for results of metals analysis ex-pressed as metal content and metal value percentages. Copper was present in highest con-tent followed by tin and lead. Copper also presented the highest value metal. Gold, palladium and nickel presented high value. Tin also presented high value for content.

1 to 2 mm size fraction - The total metal content was 577 kg per Tonne of PCB. This repres-ented a total metal value of €3716. See Table 5b in Appendix 2. Copper was present in highest content followed by tin and lead. Gold presented the highest metal value, followed by copper, despite the low content. Palladium presented high value compared to aluminium, iron and lead. The overall metal content and value for the 1 to 2 mm size fraction had increased significantly compared to <1 mm size fraction.

2 to 4mm size fraction - the total metal content was 669 kg per tonne of PCB at a total metal value of €4074. See Table 5c in Appendix 2. Copper was present in highest content followed by aluminium and iron. Gold presented the highest metal value, followed by copper and pal-ladium, despite the low content. Other metals were in low content and presented low value. The overall metal content and value for 2 to 4mm size fraction had increased compared to the <1mm and 1 to 2mm size fractions.

>4 mm Size fraction - the total metal content was 438 kg per tonne of PCB. This represented a total metal value of €1573. See Table 5d in Appendix 2. Copper was present in highest content followed by Aluminium and Iron. Copper presented the highest value metal. Gold and palladium presented high value. The overall metal content and value for the >4 mm size frac-tion had decreased compared to the 2 to 4 mm size fraction. The 2 to 4 mm size fraction presented the highest metal content and value.

PCB 5 – Passive junction boxes, lead-tin solder

<1 mm size fraction – the total metal content was determined to be 391 kg per tonne of PCB at a total metal value of €1336. See Table 6a in Appendix 2. Copper was present in highest content followed by iron, tin and lead. Copper also presented the highest value metal. Gold and tin also presented high value for content.

1 to 2 mm size fraction - the total metal content was 871 kg per tonne of PCB at a total metal value of €3002. See Table 6b in Appendix 2. Copper was present in highest content followed by tin. Gold, palladium and tin also presented high value for content. The overall metal con-



tent and value for the 1 to 2 mm size fraction had increased significantly compared to the <1 mm size fraction.

2 to 4 mm size fraction - the total metal content was 908 kg per tonne of PCB at a total metal value of €3659. See Table 6c in Appendix 2. Copper was present in highest content and presented the highest metal value. Palladium presented the high metal value. Other metals were in low content and presented low value. The overall metal content and value for the 2 to 4mm size fraction had increased compared to the <1mm and 1 to 2 mm size fractions.

>4 mm size fraction - the total metal content was 913 kg per tonne of PCB at a total metal value of €2706. See Table 6d in Appendix 2. Copper was present in highest content followed iron. Copper presented the highest value metal. Palladium presented high value compared to other metals such as Iron and Tin. Other metals were in low content and of no significant re-trievable value. The overall metal content and value for >4mm size fraction had decreased compared to the 2 to 4mm size fraction. The 2 to 4mm size fraction presented the highest metal content and value.

Discussion

In general copper was the predominant metal in terms of both content and value in almost all of the samples evaluated. Copper accounted for 65 to 90% of the total metal content followed by iron and tin accounting for, in some cases, up to 25% of the metal content. Gold, palla-dium, nickel and silver were present in the lowest contents. However, due to the high market values of gold and palladium, after copper, they accounted for the highest metal values. Cop-per value ranged from 30 to 90% of total metal value. Gold and palladium value ranged from 2 to 46% and 2.5 to 22% respectively. Aluminium, iron, silver and lead presented little value for recycling and metal recovery.

It is significant that copper accounted for the largest content and value as it is arguably the easiest to recover electrochemically. Proven technologies have been available for many years for the selective and non-selective recovery of copper from acid-based solutions con-taining mixtures of metals. Gold and palladium, however, provide a greater challenge for se-lective metal recovery because of their inertness they are more difficult to electroplate. The presence of aluminium and iron also present potential problems in that they are impossible to electroplate and also are known to hinder the metal recovery of other metals in solutions. Ideally, leachates that contain little or no aluminium and iron are more suitable for electro-chemical metal recovery.

Effect of leach out time on metals extraction

The results obtained from leach out tests and the corresponding analyses have shown that in a period of 2 to 6 hours between 80 to 100 % of the total metal content was effectively ex-tracted from the PCBs (see Table 9 and Appendix 2 - Graph 1a).



Table 9: Effect of leach out time on metals extraction content

In fact, leaching times of up to 24 hours had a negative impact on Gold and Palladium recov-ery with a reduction in the total dissolved content of these metals, possibly due to precipita-tion (see Table 10 and Appendix 2 - Graph 1b).

Table 10 Effect of leach out time on gold and palladium content

There was shown to be no significant advantage of longer leach-out times as 2, 4 and 6 hours yielded similar metal recovery results.

Effect of size fraction on metals content and value

The analysis results have shown that the fraction size used was important to metal recovery content and value. It was found that for most samples the 2 to 4 mm size fraction contained the highest content and value of recovered metals for the range of the PCBs evaluated (see Table 9 and Table 10, and Appendix 2 - graphs 2 and 3). The size fractions <1mm, 1 to 2mm and >4mm had lower metal contents and values. Copper, iron and tin followed by lead were the predominant metals in terms of content over the range of samples, with copper the most significant. Silver, gold, palladium and nickel were lower in content. However, gold and palla-dium, when present, did contribute significantly to the overall metal value due their high mar-ket values compared to other metals such as aluminium, iron and lead.



Table 11 Effect of Size fraction on metals extraction content

Table 12 Effect of size fraction on extracted metal values

Effect of lead and lead-free soldering on metal values

Although the terms lead and lead-free soldering were used to describe and distinguish vari-ous PCB types, it was not true to say the PCBs were completely free of lead, as it was found during the chemical characterisation and leach out tests. This was due to the fact that though some PCBs may not contain lead based solders, they will almost certainly still contain lead based coatings and finishes within component housings. All the samples were found to con-tain some levels of lead. The lead-free solder samples were generally found to contain less lead than the lead solder containing samples. There was found to be no significant difference in metal values for the lead and lead-free electronics currently evaluated (See Table 13). Table 13 shows the average metal values over the range of size fractions for each PCB type. The lead and lead-free electronics appear to hold similar metal retrievable values.

Table 13 Effect of lead and lead-free solder on average metal values

Development of a hierarchy of EES components for chemical recycling



All of the electronics evaluated to date hold some recyclable value. They all appeared to be similar in both content and value of metals. The leach out tests conducted proved that all the metals could be extracted effectively using acid leach out techniques. However, it is difficult to state at this time whether it is economically feasible to recover the metals chemically without a more detailed consideration of the cost of mechanical shredding, separation and electrochemical winning/recovery. It is also not yet possible to state a preference for which PCB types are more favourable from an economical perspective for recycling.

4.2.4 The lambda Sensor Study

The lambda sensor is a device that is positioned in the exhaust system of a vehicle and is used to provide information to the engine management system. It determines the air-fuel ratio and thereby increases vehicle performance and fuel efficiency whilst minimizing emissions. The mechanism in most sensors is based on a semi-conducting zirconia oxygen sensor, with platinum electrodes, which detects the air to fuel ratio which allows the engine management system to control the amount of fuel entering the engine. The zirconia cone with platinum and palladium electrodes is protected by a metallic outer casing shown in Figure 45.

Figure 45 A dismantled lambda sensor

Methodology and results

In order to verify the composition and value of the lambda sensor, analysis has been under-taken to identify the metals contents of sensors supplied by Mügu. A lambda sensor was dis-mantled to expose the zirconia cone and Energy Dispersive X-ray Analysis (EDXA) used to verify that the metal electrodes deposited onto the ceramic were platinum and palladium.



Figure 46 Metallised electrode area of the zirconia cone

Figure 47 Non-metallised body of the zirconia cone

To determine the metals content, two of the lambda sensors were subjected to acid digestion using aqua regia. A 1 ml aliquot of the resulting leachate was then diluted by a factor of twenty-five and analysed using ICP-OES. The results of the analysis are shown in Table 14.

Table 14 The results of ICP-OES

From this initial analysis data it has been found that the total value of the precious metals is approximately €1 per sensor.



Discussion

Lambda sensors contain a number of materials in their construction but the key ones from a recycling perspective are the precious metals Platinum and Palladium. These are found as the inert electrodes on the zirconia cones that form the basic sensing part of the structure. The zirconia sensor itself is contained in a metal can which requires a degree of mechanical disassembly before the sensor element can be accessed. The total value of these two metals based on prevailing precious metal prices at the time of writing is approximately €1 per sensor. The sensors examined in this study had a typical mass of approximately 79 grammes, which means that the precious metal value per metric tonne of sensors is around €12,732 The number of sensors per tonne is approximately 12,700. If it were possible to eco-nomically extract the sensor elements from the assembled units, the value per tonne of salvaged sensor elements would be much greater and is estimated to be in the region of €211,710. This increased value would obviously be offset by the additional time and costs associated with the dismantling of the complete sensor assemblies. The number of sensors required to produce one metric tonne of scrap would be approximately 210,000.

Although these are only initial studies, it appears that the value of the precious metals found in typical lambda sensors may make them an interesting potential source of materials for re-cyclers. The key to the financial success will be the cost of getting the metals into a suitable form for recycling. If recyclers require the sensor elements to be removed from the complete units there will be a cost penalty per unit in terms of the time taken for disassembly but po-tential benefits in having a more concentrated and less complex mix of materials which may make metal recovery and recycling easier and less costly. Clearly, further work is required to investigate the financial viability of lambda sensor recycling, but they do seem to offer a po-tentially valuable source of platinum and palladium.

4.3 Proposed Electrochemical metal Recovery Route

There have been numerous chemical recycling routes proposed for the recovery of materials from, end-of-life electronics and one of the more promising techniques has been developed by workers at Imperial College, London (1) (see section 4.1.5.1 for details). It is this techno-logy that is being evaluated in the SEES project. The basic approach involves the use of a novel aqueous leaching and electrowinning process for the recycling of metals such as gold, silver, copper, palladium, tin and lead. The technology employs non-selective initial dissolu-tion of the metals prior to selective electrochemical recovery. Using an electrochemical re-actor, oxidant species are generated at a titanium/ruthenium oxide anode in an acidic aqueous chloride electrolyte and these are used in a leach reactor to drive the non-selective oxidative metal dissolution. The dissolved metals can then be recovered from solution by electrodeposition at a graphite felt cathode, as the counter reaction for the anodic generation of chlorine. Hence, the overall process involves inputting electrical energy to move the metals from scrap to cathode and, in principle, produces only a de-metallised waste. The presence of metals such as Tin requires electrolytes with hydrochloric acid concentrations of greater than 1 M in order to solubilise the metal and chloride activities >1 are needed to increase sil-ver and lead solubilities, and to minimise passivation of the leaching process. The Imperial College recycling approach is shown schematically in Figure 48.



Figure 48 Schematic of the Imperial College approach

An advantage of this process is that it offers significant improvements over current pyrome-tallurgical processes and maximises metal recovery with low specific energy consumption whilst obviating the need for treating noxious gaseous emissions. A clear significance of this technology is that a single dissolution stage for all the metals contained within an input feed of shredded circuit board material can be effected within a controlled reaction environment. This avoids the inter-stage pollution and contamination problems that may be inherent in a multi-stage dissolution process, albeit with perhaps a less efficient electrolytic recovery route.

4.4 Chemical Recycling Technology

4.4.1 Process Overview and Previous Work

The general process chemistry is given in equations [4-1] to [4-5] below:

Leach reactor [4-1]

Electrochemical Reactor

Cathode (e.g. carbon felt): [4-2]

Micro-porous separator: [4-3]

Anode (e.g., Ti/RuO2): [4-4]

Overall process reaction: [4-5]



Figure 49 Schematic of the proposed leaching / electrowinning system.

It can be seen from the system flowsheet (Figure 49), that in principle, the process involves the use of electrical energy to move metals from the electronic scrap to the cathode of the electrochemical reactor, with the de-metallised scrap as the only waste stream output.

The researchers proposed that there are four main steps involved in the oxidative dissolution of metals with acidic aqueous chlorine. Chlorine gas dissolves into water to form active aqueous chlorine species. The active aqueous chlorine then transports from the bulk solu-tion to the metal surface in the scrap. The active chlorine reacts with the metals in the WEEE to form metal chloride complexes. Finally the metal chloride complexes transport away from the solid surface into the bulk solution.

Previous leaching experiments at Imperial College London were initially carried out in a 400 cm3 stirred batch reactor containing 200 cm3 of HCl and NaCl solution and between 10 and 40 g of WEEE shredded to less than 4 mm. For the base metals (Cu, Pb, Sn, Ag), a leaching conversion of greater than 99 % can be achieved in about three hours. The pre-cious dissolved metal concentrations (Au, Ag, Pd) increased more slowly; 80-95 % being dis-solved after eight hours, as shown in Figure 50. The difference in leaching rates of the metals present should be noted; the concentrations of dissolved copper, tin, and lead stabil-ised after about 200 minutes, whereas gold, silver, and palladium approached steady state values only after 490 minutes. This difference in reaction rates is likely to occur because of the different shape factors and partial encapsulation of the metals, as well as variations in re-action kinetics.

Factors that were investigated in these laboratory scale leaching experiments were the effect of the leaching solution composition, chlorine flow rate, solid to liquid ratio, and temperature on the metal leaching rates and conversion. The experiments used solution compositions ranging from 100 mol% HCl through to 20 mol% HCl / 80 mol% NaCl. As expected metal re-coveries were higher with only hydrochloric acid, but the change in composition did not not-ably affect the fraction of metal leached from the WEEE (less than 0.5 %). Increasing the total free chloride from 1 M Cl- to 5 M Cl- had more effect, increasing the overall conversion by about 5 %. Increasing the solid to liquid ratio from 0.05 to 0.2 (and hence raising the chlorine utilisation from 20 % to 80 %) resulted in a significant decrease in the dissolution rate of all the metals for the first two hours. Decreasing the chlorine flow rate from 70.6 to 26.5 cm3 min-1 produced a similar fall in metal dissolution initially. However, after sufficient



time in the reactor (about 3.5 hours), the final level of metal extraction was not affected by the variation of solid-liquid ratio or chlorine flow rate, particularly for the base metals. Figure50 shows the typical metal conversions in the leach reactor.

Figure 50: Chlorination leaching conversion from electronic scrap, (4 M HCl + 1 M NaCl, solid to liquid ratio 0.05, temperature 303ºK)

Larger scale experiments have been performed in a previous project using a continuously stirred tank reactor (CSTR) of 50 dm3 capacity charged with 20 dm3 of a 4 M HCl + 1 M NaCl aqueous solution and 4 kg of shredded electronic scrap. Again, leaching conversions varied greatly between metals, with Cu, Pb, and Sn achieving maximum values of about 0.98 after 500 minutes, by contrast Ag, Pd, and Au achieved conversions of 0.8 - 0.85 after 600 minutes. The leaching process occurred under mass transport control with respect to active chlorine for the active metals like copper, as leaching conversion was largely unaffected by variation in the stirrer rotation rate between 400 and 1200 rpm. Increased stirring rates resul-ted in small increases in metal conversions probably because of delamination of partially en-capsulated metals due to the mechanical impact of the stirrer impeller on the particles of electronic scrap. Dissolution of the precious metals was found to occur at only a fraction of the mass transport controlled rate.

This work at Imperial College London has demonstrated the possibility of removing a high percentage of metals in electronic scrap. The non-selective dissolution obviates the need for many expensive reactors and waste streams of multiple dissolution steps. The process could be important in terms of meeting targets set by the WEEE Directive because it re-moves all the hazardous metals from the WEEE and not just the valuable precious metals. On the other hand, selective recovery or further processing of the metals is required to obtain the most value from electronic scrap.

The feasibility of electrowinning of Ag, Au, Cu, Pb, Pd, Sn etc. from acidic chloride leached solutions into a graphite felt cathode of a membrane-divided electrochemical reactor has also been demonstrated by Brandon, Kelsall et al. (2). Initially a laboratory scale membrane di-vided three-electrode H-cell, fitted with a carbon felt cathode and Ti / RuO2 anode, was used to carry out batch scale electrowinning experiments on the leach liquor under potentiostatic control. Deposition potentials of 0.25V, -0.1V, -0.4V, -0.7V and -0.85V (SCE) were applied



sequentially in order to selectively deposit Au and Pd, Ag, Cu, and Sn and Pb under mass transport control. The recovery of the base metals copper, tin, and lead approached unity, with the recovery of the precious metal at about 85%. The charge efficiency was 0.99 for the deposition of copper at -0.4V (SCE). Decreasing the potential to -0.7V (SCE) resulted in the co-deposition of tin and lead; the charge efficiency was 0.85 at -0.7V, but decreased sharply to <0.01 at -0.85V, due to hydrogen evolution. Larger scale experiments were also per-formed using a three compartment electrochemical reactor made from PMMA and incorporat-ing four expanded titanium mesh electrodes under both constant potential and then constant current control. As can be seen from Figure 51, a degree of selectivity can be achieved, if re-quired, by electrode potential control.

Figure 51 Metal recovery fraction under a) galvanostatic operation b) potentiostatic operation

The previous work at Imperial College London, cited above, has firmly established the feasib-ility of an aqueous acidic chlorine leach-electrowin process for the treatment of waste elec-tronic material. The research currently underway aims to address remaining scientific and engineering issues to enable successful development of this process.

4.4.1.1 Leaching

This section of the report details the design and characterisation of the leaching process. Section 4.4.1.1.1 provides information on an oxidant suitable to leach the range of metals present in electronics, which can be re-generated. In designing the leaching process differ-ent types of leach reactors and possible flow arrangements have been considered, which are reported in Sections 4.4.1.1.2 and 4.4.1.1.3 respectively. The influence of mechanical pre-treatment processes on the ensuing chemical extraction has begun to be considered, and is detailed in Section 4.4.1.1.4.

Leaching (or solid-liquid extraction, or lixiviation) is the selective removal of components of a solid by dissolution into a liquid. The stream of solids being leached and the accompanying liquid is known as the underflow while the stream of liquid containing the leached solute is the overflow. Leaching is a multi-step heterogeneous process that involves 1) diffusion of re-actants to the particle surface; 2) adsorption; 3) surface chemical reaction; 4) desorption; and 5) diffusion of products to the bulk solution. Hence leaching is usually a continuous



multistage process because of the need to provide sufficient contact time between solvent and solids to be extracted, as well as the importance of maintaining of constant fluid flows, pressures, and temperatures. [Kirk-Othmer, 2000] (63)

It is proposed in this project to design, construct and then characterise a leach reactor sys-tem that is capable of processing 10kg of shredded electrical and electronic systems (EESs) each day. The leach reactor must meet certain process requirements in order to be suitable and cost effective for the treatment of electronic scrap:

The feed material must be pre-treated (by crushing, grinding, or shredding) to provide good solid to liquid contact such that the solvent can dissolve the extract quickly.

Only the desired material should be leached out (the process should non-selectively dissolve all the metal content of the scrap).

Economic separation of the solvent, extract solution and extraction residue must be possible. Clean de-metallised scrap (free of leach solution) should be produced, which can be sent for plastics recycling or to landfill without requiring further treatment.

The leach solution needs to be free of oxidant on exiting the reactor; any oxidant circu-lated to the electrochemical reactor will reduce current efficiency for the reduction of metals and hence increase the specific energy consumption of the process.

The system should enable the continuous production of leach liquor for the electro-chemical reactor and hence regeneration of chlorine oxidant for recycling to the leach reactor.

4.4.1.1.1 Operating Conditions

There are many factors, which must be considered when designing a leaching process, that can influence the extraction rate during leaching. These include mode of operation (batch or continuous), the contact method, particle size, choice of solvent, operating temperature, and agitation rate [Ullmann, 2000] (69). Other major parameters that must be identified when designing a leaching process are the mass fluxes of solid, liquid and gas phases, the ter -minal stream compositions, and the specific extractor equipment.

Solvent choice is principally determined by the physiochemical structure of the material to be extracted. Where a choice of solvents exist, the following criteria are likely to be considered, in approximate order of decreasing importance: solubility, selectivity, chemical/thermal stabil-ity, solvent physical properties, hazards, and cost. For particular solvents, the conditions un-der which leaching will occur (acidic vs. basic, oxidising vs. reducing) are determined from thermodynamics with the help of potential-pH (Pourbaix) diagrams. Such diagrams repres-ent the stability of a metal in a given environment by showing predominant species and phases for a fixed temperature and total dissolved activity. [Kirk-Othmer, 2000](63). For metal- chloride-water systems, the metals can be more easily leached under strongly acidic conditions. Examples of Pourbaix diagrams for copper and gold are given in Figure 52 and Figure 53.



Figure 52 Potential-pH Diagram for Au-Cl-H2O, activities: AuCln- = 10-3, Cl- = 5; 298ºK, P(Cl2)= 0.1 MPa

Figure 53 Potential-pH Diagram for the Cu-Cl-H2O System at 298 K, Cu2+ = 10-4, Cl- = 1; P(Cl2) = 0.1 MPa

The liquid chosen as a solvent should preferably have a good selectivity for the desired com-ponents. Solvent selectivity is linked to purity of the recovered extract; a purer solution re-duces the number and cost of subsequent separation units [Perry & Green, 1997] (65) How-ever, there are a large number of metals and polymers present in electrical and electronics systems that require separation and recycling, and hence it is not just a question of selectivity for a single compound. The use of many different solvents each selective for a certain metal and subsequent separate recovery will lead to a complicated leaching process and many units. However the use of non-selective dissolution and recovery will require separation and refinement of the metals at a later stage. An optimum is likely to be found in a compromise between the two set-ups. Acidic aqueous chlorine will result in the non-selective dissolution of the metals from the EESs, but the use of electrowinning allows for the possibility of semi-selective recovery of the metals.

The solubility or saturation limit of a chemical compound in a solvent refers to the maximum amount of solute that can be dissolved at constant temperature, pressure, and system com-position. Ideally, the solubility of the metals to be dissolved in the solvent should not be so low as to limit the reaction rate or require very large volumes of solvent, although this may prove difficult given the number of different metals present in EESs. The metal chloride com-plexes, present in most electronic and electrical systems, that have limited solubility are cop-per [I] chloride, silver chloride, tin [IV] chloride and lead [II] chloride. Metal ion solubility in-creases with decreasing pH and increasing chloride ions, and hence a pH < 0 and high free



chloride activities are required to dissolve otherwise passivating metal chloride films. The solubility of these species can be calculated, from thermodynamic equilibrium with the appro-priate solid precipitate(s), as a function of pH and chloride ion concentration. The solubility of copper [I] chloride is shown in Figure 53, in which the insoluble solid is CuCl at low pH and Cu2O at high pH.

Figure 54 Solubility of CuCl2-

Previous leaching experiments using acidic aqueous chlorine in a CSTR resulted typically in the concentrations of metals in the leachate solution in Table 15. However for solutions of pH=0 and a chloride ion concentration of 5M, the maximum theoretical metal concentrations are ccucl,max = 80mol m-3, cagcl,max = 7mol m-3, csncl4,max = 0.7mol m-3, cpbcl2,max = 3.5mol m-3. By com-paring the values for the concentration and solubility of the metal chloride complexes, it is ex-pected that to avoid solubility issues the leachate solution should be diluted ten times relative to the previous experiments; i.e the volume of solution required to leach the metals is ten times greater than used previously. Although the solubility listed above were only calculated for single metals in solution, and given the number of metals present in EESs the solubility of the metals may differ from the theoretical predictions, the volume of solution above can still be used for approximate sizing and costing of equipment.

Table 15 Concentration of metals in the leachate solution.

Element Concentration / mol m-3 Element Concentration / mol m-3

Cu 435.99 Mg 3.35

Al 287.31 Ag 1.62

Fe 274.10 Cr 1.45

Zn 37.97 Co 1.01

Sn 28.12 Pd 0.187

Ni 15.75 Au 0.0522

Pb 10.48 Pt 0.0308

Physical properties of the solvent should also be considered in designing a process. A low solvent surface tension facilitates solids wetting and low viscosity assists diffusion in the



solvent (the solvent becomes more viscous with time as the concentration of solute in solu-tion increases). [Coulson, Richardson et al., 2002] (49) The solvent should ideally be non-toxic and non-hazardous; adequate design must take into account the flammability and ex-plosivity characteristics of the solvent.

Operating temperature should be considered when selecting a leaching agent and designing a leaching process. Generally solubility and diffusion rates of species in a liquid increase with temperature, and hence the maximum rate of extraction may increase accordingly. However higher temperatures may require more resistant and expensive materials of con-struction to be used for the equipment, or may result in deterioration of the insoluble fraction of the solid. The solvent must also be stable at temperatures used in both the extraction and recovery process, to avoid contamination and expensive solvent losses.

Solvent agitation increases eddy diffusion (turbulence) and hence mass transfer of materials to / from the bulk solution and the solid surface. Agitation may also prevent sedimentation of the solids and maximise the use of surface area. [Coulson, Richardson et al., 2002] (49)

The ability to recover the desired components from the leaching solution and the feasibility of regenerating the leaching agent, will also affect the important choice of lixiviant. The solvent should be readily available and relatively inexpensive, as the cost of fresh solvent is reflected in the operating costs in the form of solvent make-up charges. [Ullmann, 2000].(69) Electro-chemical methods allow for the regeneration of certain oxidants, such as chlorine and nitric acid, and hence such lixiviants are advantageous as they avoid the generation of further waste streams. The non-selective dissolution of metals using acidic aqueous chlorine also obviates the need for many expensive reactors and waste streams of multiple dissolution steps.

Chlorine is soluble in water. The reactions that occur and the species that form depend on the pH (i.e. whether hydrogen or hydroxide ions are the dominant species). The species and amounts present in an aqueous chlorine system at different pH are shown in Figure 55. The concentration of aqueous chlorine is 55 mol m-3 when the partial pressure of chlorine gas is one atmosphere. Hence, for chloride concentrations of 5 kmol m-3, the trichloride ion concen-tration in equilibrium with saturated aqueous chlorine is predicted to be ca. 60 mol m-3, thereby approximately doubling the solubility of active chlorine to circa 115 mol m-3, and hence doubling the maximum transport limited reaction rates.

Figure 55 Activity-pH Diagram for Cl2-H2O System at 298ºK, chloride activity = 5M & P(Cl2) =1atm.



The choice of electrolyte influences the electrical conductivity, the electrochemical activity, and the chemical reactivity. Both HCl and NaCl provide an important source of chloride ions. Sodium chloride is less aggressive and less expensive than hydrochloric acid and in general, the addition of a salt enhances the conductivity of a solution. However the solubility of chlor-ine gas decreases with the increasing sodium chloride concentration and increases with in-creasing hydrochloric acid concentration. Another important consideration is that chlorine solubility will also decrease as the concentration of metal ions MClx in solution rises. It is thought that a leachate solution containing 1-2 mol m-3 NaCl and 3-4 mol m-3 HCl is likely to be an appropriate compromise.

The information in this section has discussed the used of chlorine as an oxidant appropriate for leaching metals from EESs, which can be re-generated electrochemically. The operating conditions are suggested as at least 5 M chloride ions, a pH of less than zero, and 100 mol m-3 dissolved chlorine concentration, to drive the dissolution of the metals in the scrap by the following reactions:

4.4.1.1.2 Leaching Equipment

There are many different types of equipment and methods of operation for leaching systems, which have different advantages and disadvantages. They may be distinguished by operat-ing cycle (batch, continuous, or multi-batch intermittent); by direction of streams (co-current, counter-current, or hybrid flow); by staging (single-stage, multistage, or differential-stage); and by method of contacting (sprayed percolation, immersed percolation, or solids disper-sion).

Leach reactors can be split into two broad categories based on the contacting method; per-colation equipment and dispersed solids (or slurry) reactors. The main difference between the two is that in dispersed solids reactors, there is agitation or stirring of the solids by pneu-matic or mechanical means.

Examples of industrial percolators are the Bollmann-type extractor, the Rotocel-type extractor and the conveyor extractor Figure 56 a+b). The solids are moved vertically in buckets or ho-rizontally on conveyors and the liquid is sprayed over the solids in successive sections in a counter-current direction. An illustration of a dispersed solids reactor is the Bonotto extractor (Figure 56 c), which consists of a column divided into cylindrical compartments by alternating hemispherical horizontal plates. The solids are caused to fall as a curtain, into the solvent that flows upwards, to each lower plate in succession by the rotating paddles. [Perry & Green, 1997]. (65)



Figure 56 a) Bollmann extractor b) conveyor extractor c) Bonotto extractor

All of the above types of leach reactor can be adapted to cope with changes to the composi-tion of scrap feedstock either by altering the flow rate of leach solution through the reactor or by altering the speed of rotation of conveyor or stirrer. Unfortunately, there is no universal optimum reactor for all reactions and operating conditions; there are advantages and disad-vantages to all the available reactors. The choice of a suitable reactor is connected to the re-quirements and characteristics of the process and the engineering aspects.

Dispersed solids reactors are efficient if the agitator just gently circulates the solids across the tank bottom or barely suspends them above the bottom. In slurry reactors the solids are dispersed and (partially) suspended in the liquid and must subsequently be separated from it, requiring additional time and costs of operation. The movement of hard particles may result in abrasion of the equipment in dispersed solid leaching (stirs, tubes, pumps, etc.) as well as abrasion of the solid surfaces. Breakdown of the solids may be advantageous in aiding the extraction rate, but the generation of fine particles may result in further difficulties in separa-tion of the solid and fluid phases. Stirred reactors generally have a high liquid hold-up, a good solid-liquid contact, and a low solid to liquid ratio. Consequently, they are of particular interest for highly exothermic reactions and temperature control necessary to avoid hotspots and runaway reactions. However such reactors constitute only a single equilibrium stage and have a low specific productivity per unit volume. A quasi-multistage leaching process with slurry reactors is possible by using a number of reactors in series, with the fresh leach solution being introduced to the tank containing the most depleted solid, although the com-plexity of organising such a process, with numerous solid-liquid separation stages, is another limitation. [Biardi & Baldi, 1999], (44) [Datsevich & Muhkortov, 2004](51)

The choice of a percolation or solids dispersion technique for leaching depends principally on the amenability of the extraction to effective, sufficiently rapid percolation. (For a percolation system to be viable, the extraction rate needs to be high, as the solvent residence time is often relatively short.) Percolation reactors have a large concentration driving force and mul-tiple equilibrium stages along their length. As the void fraction with respect to the solid is also lower, the volume of a packed bed reactor should be considerably smaller than a stirred tank reactor to process 10 kg of EESs. There are a number of disadvantages of fixed bed multiphase reactors, due to the large solid particles utilised. Poor fluid phase distribution



(channelling / deadspots) may affect the performance of the reactor positively or negatively; gas and liquid distributors may be needed inside the reactor to avoid this. A higher reaction pressure and/or temperature may be required due inefficient solid-liquid-gas mass transfer. Although it is not applicable to the leaching of metals from electronics, in case of highly exo-thermic reactions, a drawback is represented by poor temperature control. As the major dis-advantages for percolation reactors either do not apply or may actually be advantageous, it is considered that packed bed reactors are likely to yield the best performance for this project.

As mentioned previously, the chlorine in the leach solution must be completely depleted on exiting the reactor to avoid loss of efficiency in the electrowinning process and the residence time of materials in the reactor must be sufficient to ensure this. However, in a percolation reactor, the rate of reaction will initially be highest at the reactor entrance, due to the concen-tration of the oxidant chlorine and the metals to be leached. As a result, the concentration of solid metals decreases more rapidly at the start of the reactor, and so the reaction zone will move along the reactor length with time. Hence if the reactor length and gas flowrate are se-lected to ensure the chlorine is depleted initially, breakthrough of the oxidant will occur as the reaction zone moves along the column, shortening the effective reactor length with time. It will therefore be necessary to recycle the unreacted chlorine / leach solution or utilise a second reactor towards the end of the operation.

The choice between continuous and batch operation is largely a matter of the size and nature of the process of which the extraction is a part. The following factors are likely to affect mode of operation: production rates; flexibility requirements (seasonal, technological); operational needs (fouling, slow reaction); range and lifetime of products. Continuous processes operate 24 hours a day, 7 days a week and only shutdown for maintenance and emergency, whereas batch processes stop to fill, empty and clean the reactors between each operation. As con-tinuous operation avoids the frequent periodic loading and unloading of material from batch reactors, it is often preferred for large-scale processes. Small capacity plants less than106

kg/yr are usually batch, while a larger capacity of more than 107 kg/yr favours a continuous route. Equipment that allows the movement of solids through a leach system is mechanically complex, requiring large capital expenditure and regular maintenance, and is probably not justified for a system to process only 10 kg or 100 kg of shredded WEEE per day. [Douglas, 1988](52)

A possible compromise between a batch process with large downtime and an expensive con-tinuous process, suggested by [Stevens & Lansdowne, 2003] (68) and [Percival & Thomson, 2004] (64), is to utilize three reactors in a continual mode, as shown in Figure 57. At any one time, the fluid flows consecutively through two of the reactors, while the third reactor is off-line being emptied and refilled with fresh metal scrap.



Figure 57 Schematic of leach system to allow quasi-continuous leaching

As discussed above, it is proposed that a packed bed reactor operating in continual mode is likely to yield the best performance for the leaching of metals from EESs. Hence this is the type of reactor which is being designed and on which further experiments are being per-formed.

4.4.1.1.3 Packed Bed Reactors - Flow Arrangement

With respect to the movement of gas and liquid streams and assuming a stationary solid phase, percolation reactors processing solid, liquid and gas reactants can operate in three modes: downward co-current flow (trickle-bed reactor), in upward co-current flow (bubble column), and in counter-current flow, as shown in Figure 58.

Figure 58 Modes of operation for percolation reactors [Dudukovic, Larachi et al., 1999](53)

Counter-current operation is favourable in terms of phase and reaction equilibrium; conven-tional gas–liquid absorbers operate in this mode to maximize the driving force for gas–liquid



mass transfer. Problems with counter-current operation, however, are excessive pressure drop (requiring high voidage packing to compensate) and flooding at low fluid superficial ve-locities. At the flooding point, the counter-current flow of vapour and liquid in the column breaks down, as the liquid builds up in the packing and is pushed upward by the vapour. Hence fixed bed reactors are mostly employed with co-current flows of gas and liquid to avoid the hydrodynamic limitation of flooding.

Depending on the flow rates of the fluid phases, there are a number of define flow regimes for co-current flow

spray flow (liquid droplets and continuous gas phase), trickle flow (one directional liquid rivulets and continuous gas phase), pulse flow (intermittent gas- and liquid-rich zones ), bubble flow (continuous liquid and dispersed gas phase)

In trickle-bed reactors (TBR) the liquid trickles down over the solid in a film or in channels, while the gas flows co-currently down the void spaces. In a packed bubble column reactor (PBC) the liquid flows upwards in a continuous phase and the gas bubbles upwards through it.

Downward flows are more widely used on an industrial scale than upward flows, because the pressure drop and liquid hold-up are much less (the hydrostatic head of the liquid must be overcome in upflow). To provide general advice on which reactor type to choose, [Khadilkar, Wu et al., 1996] (61) and [Dudukovic, Larachi et al., 2002](54), examined the previous stud-ies for flow arrangements in packed beds and concluded that:

Co-current flow downflow should generally be chosen at low liquid and gas superficial velocities but that upflow is superior at higher liquid and gas velocities

For liquid limited reactions, upflow is preferred as it provides complete solids wetting and the fastest transfer of liquid to the solid surface.

For gas limited reactions, downflow reactors, especially at partially wetted conditions, are preferred, as they facilitate the transport of gaseous species to the solid surface.

Flow maldistribution and incomplete solid-liquid contacting effectiveness is common, espe-cially in the trickle flow regime. At any moment in time, parts of the solid surface will usually be in contact with flowing rivulets, parts covered by a very thin liquid film, parts in direct con-tact with the gas phase, and parts within dead zones (Figure 59). This liquid maldistribution may be due to either the reactor scale (and so portions of the reactor do not contain liquid) or the particle scales (and hence the liquid flow rate is insufficient to cover all the catalyst particles with a continuous liquid film at all times). As noted above, if the key reactant is a li -quid, the reaction rate may be more affected by diffusion phenomena and may be slower than that in an evenly wetted particle. However gaseous reactants like chlorine are fed more efficiently to the solid through the unwetted zones, and hence if the key reactant is present as a gas, an increase in reaction rate may be perceived.



Figure 59 Distribution of liquid in a trickle bed reactor [Biardi & Baldi, 1999](44)

Although it is expected from the general comparisons in the literature that a packed trickled bed reactor is the most suitable type, the mass transfer coefficients and pressure drop will be evaluated using the correlations listed below, to aid in the selection of the most effective leach reactor

No method to determine the pressure drop and liquid hold-up emerges as clearly superior, but semi-theoretical and phenomenological models seem more reliable than strictly empirical correlations. For trickle bed reactors the extended slit model of [Iliuta, Larachi et al., 1998] (59) is recommended. It can be noted that generally, at a given density, the two-phase pres-sure drop increases with gas and liquid mass fluxes, superficial velocities and liquid viscosity. Liquid hold-up increases with liquid mass flux, superficial velocity, and viscosity, but de-creases with increasingly gas mass flux or superficial velocity. It has also been observed that liquid hold-up and two-phase pressure drop increase substantially in beds where fine (< 1 mm) are mixed with the larger size particles.

It has been found that for a given gas density, gas–liquid interfacial areas and volumetric li-quid side mass transfer coefficients increase as liquid and gas mass fluxes or superficial ve-locities increase. Mass transfer parameters improve in both TBRs and PBCs as the gas density increases for given gas and liquid superficial velocities. The suggested correlations for general design purposes are that of [Iliuta, Ortiz-Arroyo et al., 1999] (60), in the form of a neural network, which have been validated over broad ranges of experimental gas–liquid mass transfer data (3200 experiments for 52 gas-liquid systems, 60 packing sizes and geo-metries, and 17 column diameters).

The initial calculations are in agreement with the general recommendations in the literature; the gas-solid mass transfer coefficient for leaching in a trickle bed reactor is several orders of magnitude higher than the liquid-solid mass transfer coefficient in a bubble column reactor. However, it should be noted that the predicted gas-liquid mass transfer coefficient is higher in a PBC than a TBR. Hence, a leach reactor flow circuit has being constructed (Figure 60) which is flexible in set-up, so that the effects of different flow configurations (trickle bed, bubble column, and counter-current gas and liquid flows) on reactor performance can be compared in the next reporting period.



Figure 60 Packed column leaching reactor system

4.4.1.1.4 Packed Bed Reactors - Shredding Size

For chemical recycling to be efficient with modern day multi-layer printed circuit boards, a sig-nificant degree of dismantling and mechanical separation will be required before chemical technology can be utilised. Hence this section provides details of the effect of mechanical pre-treatment on the leaching process that is being considered.

The main steps in the mechanical treatment of electronic scrap are the size reduction of com-ponents and the separation of different material fractions. Size reduction may occur by the use of shredders, which shear material between adjacent rotating discs; grinders in which the cutting action of rotating and stationary knife blades; and hammer mills, which involve impact size reduction. Air cyclones are used during size reduction to remove foam, plastic, dirt, fab-ric, rust, rubber, and paint (currently for sent to landfill). Mechanical separation processes may involve gravity separation (differentiate between plastics and metals), magnetic separa-tion (to remove ferrous metals iron & steel) and eddy current separation (to separate metallic and non-metallic materials). [Cui & Forssberg, 2003] (50). An example of a mechanical treatment route is given in Figure 61.



Figure 61 Flow chart for mechanical processing of electronic waste

A trade off exists between the degree of mechanical segregation and the efficiency of chem-ical leaching. A higher level of mechanical separation will have higher costs and possibly in-creased metal losses in the non-metallic fractions, but the chemical dissolution will be im-proved, as the oxidants will have better access to the metals (especially when encapsulated metals are liberated by mechanical shredding). The efficiency of subsequent pyrometallur-gical or hydrometallurgical technology is increased by the use of mechanical separation pro-cesses, but about 10 % of the valuable precious metal content is normally lost [Goosey & Kellner, 2002] (57). Smaller particles give rise to a greater interfacial area and smaller dis-tances over which diffusion must occur, which lead to higher rates of mass transfer and gen-erally favour rate of the leaching process. However very small particle sizes (less than about 200 mesh) may limit the liquid circulation in percolation reactors or the solids flow in counter-current operation. Liquid solid separation and lower drainage rates from the solid residue may also present a problem with small particles [Coulson, Richardson et al., 2002].(49) Hence a compromise has to be made to select a particle size, which is producible at an ac-ceptable cost, offers a suitable extraction rate, but does not unduly impede solid and/or fluid movement.

Printed circuit boards from electronic junction boxes supplied by LEAR have been shredded to less than 6mm by GAIKER and characterised (see section 4.2). For the purpose of study-ing the effect of shredding size on the leaching of metals from EESs using a packed column reactor, the automotive junction boxes were sorted into five size fractions. The weight per-centage contribution of the size fractions to the total scrap and the distribution of metals within the size fractions are shown in Figure 62. It can be seen that in comparison to the cop-per present, the fraction of base metals (such as aluminium, iron, tin, and lead) is higher for the smaller particles.



Figure 62 Distribution of size fractions and metals within shredded EESs shredded to < 6mm

To determine appropriate experimental conditions in the leach reactor and avoid many time-consuming inoperable experimental runs, the maximum flow rate achievable through different size fractions was determined using a smaller column to that used in the leaching experi-ments. The column was filled with a known volume of pre-wetted particles and the average time for 100 ml of water to pass through the column was measured. Figure 63 shows that for the material considered thus far, the smallest size fraction containing fines (found to consti-tute 10 % by volume of a typical shredded scrap sample) has significant plugging potential and may be more efficiently recovered in a stirred reactor.

Figure 63 Maximum flow rate through different scrap size fractions

For the leaching experiments shown in Figure 60, 0.5 kg of shredded electronics was added to the leach column, which was operated in trickle bed mode, and 10 L of 4 M HCl and 1 M NaCl leaching solution was charged to the reservoir. Based on theoretical predicted solubilit-ies, this volume of solution should prevent operational issues arising from exceeding the sol-ubility limits of the metal chloride complexes in solution. The electrowinning cell used to gen-



erate chlorine gas was filled with an acid solution similar to that used in the leaching reser-voir, and was connected to a 10 Amp Autolab potentiostat.

The acidified chlorine solution on contact with the particles at the top of the column removed the oxide layers rapidly revealing shiny metal surfaces (this contrast was particularly visible between black copper oxide and pink copper metal). Initially, the oxidant was depleted in the inlet section of the reactor and so metal did not dissolve so quickly along the length of the column, but as the quantity of reactant in the initial sections depleted the reaction “zone” gradually moved down the column.

It can be seen in Figure 64 that a decrease in particle size (which produces an increase in the interfacial area) increased the leaching rate, especially for copper. Hence, the total time required to leach all the metals (including the precious metals) from the electronic scrap, in-creased with particle size. However, for the particle sizes considered thus far, encapsulation was not found to be a problem, and hence milling the EESs to smaller pieces did not liberate significantly more metals. Therefore, for electronics shredded to less than 6mm, the extent to which metals dissolved was not affected given additional leaching time.

Figure 64 Leaching of copper, tin and lead from EESs shredded to 1.25-2.5mm and 3.5-6.5mm.

An important point observed during the leaching experiments is that although the dissolution of metals with chlorine non-selective, the metals do not dissolve at the same rates. The most active metals such as iron and aluminium, which will react with the concentrated acid, are re-moved most rapidly. Tin and lead also increase in concentration in the leachate before less active metals like copper and silver. This is most likely because copper ions that are leached at the top of the reactor, when the chlorine is present at a high concentration, may redeposit further down the reactor to dissolve more active metals.

When operating a large scale process it will not be desirable to sort shredded electronics into numerous different size streams. It is expected that splitting the mechanically treated EESs into two, and leaching the smaller particles in an agitated reactor and the larger ones in a packed column may be the most cost efficient option. Hence, the next step in optimising the process for the recovery of metals from printed circuit boards, is to obtain EESs shredded to



different maximum sizes (for example 5mm, 10mm, and 15 mm) and treat the material as just one or two types within each size.

4.4.1.2 Modelling of the Leach Reactor

It is also desired to devise a model for the performance of the leach reactor that predicts the conversion of the oxidant chlorine; metal conversion from the scrap; concentration profiles of species in the reactor; and the time for breakthrough of oxidant, as the reaction zone moves down the reactor. It is recommended that some of the current uncertainties be addressed and incorporated into the model to predict the behaviour of a leach reactor. These include the time-dependent areas for the complex geometries for each of the metals and extents of encapsulation / liberation. The electronic connections between two or more metals with dif-ferent electrochemical behaviour, resulting in selective dissolution of the more active metals or displacement reactions between metals of different activities should also be considered. The metal leaching rates can be determined at rotating disc electrodes confirming or remov-ing the current assumption that dissolution of the metals is limited by mass transport control. This work will be presented in the next reporting period.

This work has been performed at Imperial College London as part of an EPSRC funded pro-ject [Cheng, Kelsall et al, 2006] (48). Models were developed for a packed bed leach reactor for dissolving metals (Ag, Au, Cu, Pb, Pd, Sn) from waste electrical and electronic equipment (WEEE) by dissolved chlorine in acidic aqueous chloride solutions, the dissolution kinetics of non-precious metals being controlled by the mass transport of chlorine. Three particles shapes of shredded WEEE (sphere, cylinder, triclinic prism) were considered and the time evolution of metal surface area was computed using finite element software. The effects were calculated of particle shape, liquid flow rate, operational mode (single-pass and part batch recycle) and reaction rate coefficients for precious metals, on metal conversion and ef-flux chlorine concentration. For Re = 2.4, overall metal conversions of > 0.9 were predicted to be achieved in 8 hours with single-pass mode, ‘breakthrough’ occurring for metal conver-sions > 0.6, and in 10 hours with part batch recycle mode.

4.4.1.3 Electrowinning

The possibility of electrowinning of Ag, Au, Cu, Pb, Pd and Sn from leach solutions, into the graphite felt cathode of a membrane-divided electrochemical reactor, has been shown. To operate the process at pilot-plant or industrial scale for any length of time at, it is also neces-sary to consider what leached species cannot be electrowon and so accumulate in the elec-trolyte. An electrowinning reactor is being designed and built to determine this by exhaustive electrolyses, as well as whether the metals that cannot be won affect the electrodeposition process. Possible solutions in how best to bleed and recover them, e.g. by precipitation with lime, will also be examined. This work is described in Section 4.4.1.3.1.

The rate of conversion in electrochemical cells is proportional to the electrode surface area, the mass transport coefficient, and the concentration of metal to be electrowon. Due to the low concentration of the precious metals in WEEE/EESs, a three-dimensional cathode, with a high surface area per unit volume and/or good mass transport characteristics, is required for the recovery of metals from the leachate by electrodeposition.



The feasibility of using graphite-felt cathodes has been established experimentally and theor-etically for simultaneous deposition of the range of metals in the leach solutions. Although they are relatively simple design, they suffer from several limitations:

Require mechanical support and feeder electrodes;

Are difficult to remove from a reactor to harvest the powdery alloy product;

Suffer increasing pressure drop across the felt with time;

Rapid loss of surface area due to clogging.

Hence, possible alternative three dimensional cathode designs are explored for continuous / continual removal of metallic products, in Section 4.4.1.3.2.

During the initial electrowinning experiments of the process development, the electrochem-ical reactor was not coupled to a leach reactor. For both of the investigations described above the electrochemical reactors were operated in batch recycle mode with electrolyte reservoirs and oxygen rather than chlorine generated at the anode of the reactor. A schem-atic of the reactor and flow circuit used for the experiments described above is shown in Fig-ure 65.

Figure 65 Electrochemical reactor flow circuit.

4.4.1.3.1 Exhaustive Electrolysis

For the purpose of determining what leached species cannot be electrowon an electrochem-ical reactor made from polymethylmethacrylate (PMMA) was used. The reactor was divided by a fluorinated cation-permeable membrane, and operated under both constant potential and constant current control. The volume of each of the anode and cathode compartments of the reactor was 0.5dm3, and the total volume of anoltye and catholyte circulating in each system was 2 dm3. The leach solution of composition given in Table 16 was used as the catholyte, from which metals were deposited at a carbon felt cathode (210 mm(h) × 50 mm(w) × 10 mm(d)) backed by a Ti mesh electrode. The cathode potential was controlled



with a Luggin capillary probe containing a saturated calomel reference electrode (SCE), as-sumed to have a potential of +0.245 V (SHE). The anode used to generate oxygen from an anolyte of 4 M H2SO4, was a dimensionally stable anode (DSA), consisting of titanium mesh with RuO2 + TiO2 electrocatalyst (210 mm(h)× 50 mm(w)). Control of the current supplied to (or the operating potential of) the electrowinning reactor was achieved with a 10 A / 30 V Autolab potentiostat. A schematic of the carbon felt reactor and a photograph of the reactor flow circuit are shown in Figure 66.

Table 16 Catholyte Solution Composition.

Element Concentration / mol m-3 Element Concentration / mol m-3

Cu 435.99 Mg 3.35

Al 287.31 Ag 1.62

Fe 274.10 Cr 1.45

Zn 37.97 Co 1.01

Sn 28.12 Pd 0.18

Ni 15.75 Au 0.0522

Pb 10.48 Pt 0.0308

Figure 66 Electrochemical reactor and flow circuit operated in batch recycle mode.

The carbon felt reactor was operated for a total of twelve hours under both potentiostatic and galvanostatic control. The cathode feeder electrode potential was controlled with respect to a saturated calomel electrode (SCE) at potentials -0.4V, -0.5V, -0.6V, -0.65V, and -0.75V.



For galvanostatic control, the total current was fixed at 9A and the potential range dropped from -0.5V to -0.85V.

Under these conditions metals that can be won from the leach solution at high current effi-ciencies are copper, tin, lead, palladium, silver, gold, and barium. Complete recovery of the dominant copper and the precious metals at potentials below -0.5 V (SCE) can be seen in Figure 67. Recovery of considerable amounts of tin and lead was possible after the copper had been eliminated (as shown in Figure 67). As will be discussed in Section 4.4.2, the lack of online measurement of the dissolved metal concentration meant that the experiments were stopped before all of the tin and lead were removed. However, it is realistic to expect that complete removal of the tin and lead is possible by electrowinning at potentials below -0.65 V (SCE) for longer periods of about three hours.

As can be seen from Figure 67, approximately 20% of the zinc, iron, and nickel deposited, catalysing hydrogen evolution and decreasing current efficiencies. This deposition would not be predicted for the individual metals at pH = 0 and [Cl-] = 5 M, even at the lowest potential that was utilised of -0.75 V (SCE). It is thought that the zinc, nickel, and iron were recovered as a result of alloy formation, probably with the depositing tin and lead. As it is not possible to reduce Al(III) from aqueous solutions, no depletion of its concentration was measured.

Figure 67 Concentration of Cu, Fe, Al, Pb, Sn. Zn, Ni, Pt, Ag, and Pd in solution during electrowinning with a carbon felt reactor

The largest loss of efficiency during electrowinning of Pb, Ni, Fe etc from aqueous solutions is the reduction of hydrogen. As can been seen from Figure 68, the current density for hy-drogen evolution varies over many orders of magnitude for different metals. This is because the hydrogen bonds should not be too weak such that the hydrogen is unstable on the sur-face nor too strong leaving few sites available for H + H recombination. This can be demon-strated with a metal hydrogen bond strength "volcano" diagram in which metal hydrogen bonds on the right hand side of the volcano peak are too strong while those on the left hand side are too weak. Metals such as platinum, iron, and nickel near the peak of the volcano



are good catalysts for hydrogen evolution, but other metals like lead may actually pacify hy-drogen reduction.

Figure 68 Kinetics of hydrogen evolution on metals.

A possibility for the recovery of aluminium is to raise the pH with the addition of lime, and pre-cipitate the metal as Al(OH)3. As the equilibrium potential for hydrogen evolution, and hence the overpotential for hydrogen evolution on metals, is dependant on pH, this gives the option of electrowinning metals such as iron and nickel at much higher current efficiencies. It should also be noted that, unlike the samples of shredded electronic equipment used in these experiments, iron and aluminium can be removed from the waste stream during mech-anical pre-treatment and sorting stage. Hence, because they are only present in the shred-ded EES in very small quantities, the recovery of the metals from solution is not as critical as these results might suggest, as was found with the EESs used for the leaching experiments in Section 4.4.1.1.4.

The deposition of copper, tin and lead under both galvanostatic and potentiostatic control are compared in Figure 69. Operating under constant current (galvanostatically) means that semi-selective deposition of the metals on the cathode is achievable. The potential is auto-matically adjusted to deposit metals in order of descending equilibrium potential. (As the concentration of copper is reduced the potential falls to maintain the copper reaction rate and hence current generated. Once the copper has been depleted the potential falls further until another metal, or hydrogen, begins to be reduced to continue generating the desired cur-rent.) As can be seen from the graphs the main drawback of the galvanostatic method, is that the metals deposit at lower potentials and hence a lower current efficiency results. For metals with multiple oxidation states, it is also believed that initially partial reduction of the metals takes place. Dark mixed oxidation solutions are produced, most likely as a result of partial oxidation of Cu[II} to Cu[I], although experiments to better understand the process chemistry and determine exactly which species are involved are underway [Igbene, 2005] (58). Only when Cu2+ has been depleted does the reduction of Cu+ to metallic copper take place. Potentiostatic control allows the choice between selective or non-selective deposition, although setting the potential at a value (V=-0.7 V) that would allow deposition of most metals would result in a considerable amount of hydrogen evolution at the cathode, that would again



decrease the current efficiency. From the results obtained, it is thought that semi-selective electrowinning at a variety of potentials (e.g. V1 = -0.5 V, V2 = -0.7 V) is the most efficient method of metal recovery.

Figure 69 Metal recovery during potentiostatic and galvanostatic electrowinning.

To conclude this section, it has been found that semi-selective electrowinning at a variety of potentials (e.g. V1 = -0.5 V, V2 = -0.7 V) is the most efficient method of metal recovery. It has also been shown by exhaustive electrolysis that complete recovery of copper, silver, gold and palladium is possible from the leachate solution in about six hours, at potentials below -0.4 V (SCE), with a high current efficiency. The potential can then be stepped down to below -0.6 V (SCE), for essentially complete removal of the tin and lead within a further three hours (also at high current efficiency as both metals are poor catalysts for the evolution of hydro-gen). During the electrowinning experiments, approximately 20% of the zinc, iron, and nickel deposited as a result of alloy formations, catalysing hydrogen evolution and decreasing cur-rent efficiencies. No depletion of the aluminium concentration was measured during exhaust-ive electrolysis, as it is not possible to reduce it from aqueous solutions.

4.4.1.3.2 Electrochemical Reactor Cathode Type

As mentioned previously graphite-felt cathodes have a number of drawbacks for the use of metal recovery from WEEE including clogging and dendrite formation. These are the norm when copper is electrodeposited on plate electrodes from chloride media, causing shedding and re-oxidation of the copper product. As an alternative reactor design, the behaviour of a circulating particulate bed cathode reactor, using copper beads in contact with a copper plate feeder electrode, and borrowed from another project, was tested. An advantage of this design, as compared to the carbon-felt reactor, is that it can be more readily adapted for con-tinual removal of the metals by increasing the liquid flow rate and blowing the beads out of the reactor. Moreover, the movement of the particles could inhibit the formation of dendrites and the subsequent re-dissolution of the metal, a problem encountered with the carbon felt reactor. A schematic and photographs circulating packed bed reactor are given in Figure 70 and Figure 71.



Figure 70 Schematic of the circulating particulate bed electrochemical reactor.

Figure 71 Photographs of the circulating particulate bed electrochemical reactor

Improved mass transport and thus increased current density by setting the electrodes in mo-tion or by applying turbulence promoters. Examples are the pump cell, the Chemelec cell, the ECO cell, the beat rod cell, and cells with vibrating electrodes or electrolytes. Attempts to accommodate large electrode area in a small cell volume resulted in developments such as the multiple cathode cell, the Swiss roll, or the extended surface electrolysis (ESE) cells. Im-proved mass transfer coefficients and enlarged specific electrode area are provided by the use of three-dimensional electrodes. Examples are the porous flow-through cell, the RETEC cell, the packed-bed cell, the fluidized bed cell, and the rolling tube cell.



Due to the higher conductivity of the copper beads and the improved mass transport charac-teristics as compared to the carbon felt, the current required was higher for this reactor design. The initial leachate solution was therefore diluted and the experiment constituted adding known (but increasing) quantities of leachate solution into 2 Lt of 4 M HCl and ob-serving the time required each time to deplete the metals from the solution. The experiment was run under potentiostatic control at -0.5V.

An interesting observation is that regardless of the fact that an increasing amount of metal solution was added at each cycle, the time required for the reduction of the copper was ap-proximately the same suggesting some degree of mass transport control (Figure 72). It is unlikely that all of the reactions are mass transport limited however, because the total current generated was not linearly related to the volume of leachate (mass of metals) added. In ad-dition, the current always reached a specific value of -0.4A after the depletion of the metals, which is likely due to hydrogen evolution. Other metals won with this reactor where again Pd, Ag, Au and Ba, while approximately 20% of Sn and Pb were recovered (Figure 72). Only a fraction of the tin and lead were recovered as the operating potential of -0.5 V (SCE), chosen to demonstrate the feasibility of metal recovery with this reactor type, was not low enough to reduce them.

Another remark that can be made from Figure 72 is that the amount of Fe and Al kept in-creasing at each cycle, as these metals accumulate in the electrolyte. As this experiment is a good representation of the system when the two reactors (leaching and winning) will be coupled, the need for alternative means of removal of these metals is clearly demonstrated.

Figure 72 Concentration of Cu, Fe, Al, Pb, Sn. Zn, Ni, Pt, Ag, and Pd in solution during electrowinning with a circulating particulate bed reactor

Overall the results obtained from the two reactors are promising and have provided some useful observations for the improvement of the reactor design and the understanding of the



process chemistry. With the circulating particulate bed cathode, copper was rapidly depleted from solution by electrodeposition onto (growing) copper beads and dendrite formation was very limited. Hence, a new such reactor will be designed and built to be able to process 10 kg WEEE day-1, and its behaviour more fully characterised.

Potential, current density and hence metal concentration vary within a three dimensional electrode, and hence a one dimensional mathematical model in Maple has been used to pre-dict the potential and concentration distribution within the three dimensional reactor. This model has been used to predict the recovery of both gold [Robson, Kelsall et al, 2006](66) and copper from solution. It can be seen in Figure 73 that to avoid a large potential drop across a 1 cm deep particulate cathode bed, it is necessary to maintain metal concentrations below 100 mol m-3. Recently, as part of an EPSRC funded project at Imperial College Lon-don, further improvements to modelling of the circulating particulate bed cathode reactor have been made, to incorporate to a two dimensional mathematical model and to account for the flow patterns and variable flow rates within the reactor.

The results from the initial experiments and the model predictions have been used to design a reactor in AutoCAD Figure 74) that is able to process 10 kg WEEE day-1 and matches the process needs.

Figure 73 Effect of copper(II) concentrations on the potential profile predicted by 1-D model of the circulating particulate bed cathode



Figure 74 Electrochemical reactor incorporating circulating particulate bed cathode for metal recovery

This reactor design has been manufactured from polyvinyldifluodide (PVDF) (with glass view-ports) in the Chemical Engineering Department Workshop at Imperial College London. The anode was manufactured by Magneto from DSA (mixed metal oxide) mesh and a titanium frame. The cathode is a 2mm thick sheet of either copper or titanium. Silicone sheeting between the main sections of the reactor (cathode back, cathode compartment, anode com-partment, and anode back) is used to seal the reactor, which is closed by use of a lacquered aluminium frame. The new reactor, shown in use in Figure 75, has now been commissioned and also shown to be able to deplete copper from solution for several continuously.

Figure 75 Photographs of the new circulating particulate bed electrochemical reactor in operation

4.4.2 Process Control

An important aspect in scaling up the system is online measurement and analysis of the pro-cess variables (such as temperature, pressure, flow rate, and concentration) to enable good process control. Details of the development of sensors for process control are given in this section.

It is interesting to note that studies of the leaching and electrowinning have thus far been car-ried out as separate processes. The scrap was leached in a batch reactor and then the metals are recovered in a batch electrochemical system, without continuous interaction between the two systems. An important requirement in coupling the leach and electrowin-ning reactors is measurement of the dissolved chlorine concentration. To achieve high cur-



rent efficiencies for metal deposition, it is important to ensure that chlorine generated at the anode of the electrochemical reactor is completely consumed in the leach reactor. If re-turned to the cathode of the electrochemical reactor, it would be reduced in parallel with metal deposition causing loss in effective current efficiencies and an increase in electrical en-ergy consumption.

Measurement of the metal ion concentration in solution also allows the rate and extent of both the dissolution of the metals from the WEEE, and their subsequent recovery from the leachate solution, to be followed. Currently these measurements are performed by induct-ively coupled plasma (ICP) spectrometry, which is very accurate down to parts per billion levels, but involves taking samples and analysing the solutions after the experiments have been completed. Hence, on-line spectrophotometric and voltammetric measurements of dis-solved metal ion and chlorine concentrations are being developed for improved process con-trol.

4.4.2.1 Spectrophotometry

Electromagnetic radiation is a wave propagating in space with electric and magnetic compon-ents, which oscillate at right angles to each other and to the direction of propagation. Elec-tromagnetic radiation travels at the velocity of light (c), and is characterized by its frequency () or its wavelength ().

[4-6]

The electromagnetic spectrum (Figure 76) ranges from high-energy cosmic rays (high fre-quency, short wavelength) to very low-energy microwaves (low frequency, long wavelength). Visible light represents a very narrow section of this range with wavelengths between 400 nm for blue light and 780 nm for red light. Shorter wavelengths (180 – 400 nm) fall into the ultra-violet region and longer wavelengths (0.8 – 1000 m) are in the infrared region.

Figure 76 Electromagnetic spectrum.

The molecular energy of a system may be approximated as the product of an electronic, vi-brational, and rotational component, transitions between these discrete energy levels may occur upon interaction with electromagnetic radiation (Figure 77). The transitions can be



electronic (involving changes in the distribution of electrons about atoms or molecules), vibra-tional (changes the bond length of molecules), or rotational (changes to energy of a molecule rotating about its centre of gravity.

Figure 77 Electronic energy transitions

Figure 78 Spectra of molecules

When radiation interacts with matter, several phenomena may occur: reflection; diffraction (scattering); absorbance; fluorescence (absorption and re-emission); and photochemical re-action (absorbance and bond breaking). Spectroscopy is the study of the spectra that may arise as a result of the interaction with electromagnetic radiation. The spectrum of an object is the distribution of light along the electromagnetic spectrum, and is determined by the ob-ject's composition. An example is shown in Figure 78

Infrared spectrophotometry is often used to determine the presence of distinct functional groups in organic molecules. Identification is possible because infrared (IR) radiation causes different function groups to vibrate at various frequencies. Ultraviolet and/or visible spectro-



photometry are used primarily to identify how much (quantitative analysis) of a substance is present, usually in a solution, by relating the concentration to the absorbance with Beer's law. X-ray spectroscopy is used in surface science or materials science to analyze the top few atomic layers of a substance and determine chemically what elements are present and occa-sionally what the structure is.

A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the in-tensity of light reaching a detector; see Figure 79. Traditionally a spectrophotometer consists of a light source, a monochromator (a series of prisms and slits to create light of a single wavelength), and a photoelectric detector, which produces a readout signal. A spectrum for the whole wavelength range under consideration can be obtained with the use of a polychro-mator (a dispersion prism) and a multi-channel diode array.

Figure 79 Spectrophotometer arrangement a) monochromatic b) polychromatic



One of the most common applications of spectrophotometry is to determine the concentration of an analyte in a solution. The percentage of light that passes through the sample (in com-parison to a blank) is known as the transmittance (T) and can be calculated from the Beer-Lambert law [4-7]. The absorbance (A) represents the amount of light absorbed by the sample and is given from equation [4-8].

[4-7]

[4-8]

The absorbance of a sample varies linearly with both the cell path length (l) and the analyte concentration (ci). These two relationships can be combined to yield the equation [4-9] called Beer's Law.

[4-9]

The quantity is the molar absorptivity, which varies with the wavelength of light used in the measurement. Hence the extent to which a sample absorbs light depends strongly upon the wavelength of light, which is known as the absorbance spectrum. To obtain the highest sensitivity and to minimize deviations from Beer's Law spectrophotometry is usually per-formed using monochromatic light, in which all photons have the same wavelength (max) at which the absorbance is the greatest. The wavelength of max is characteristic of each com-pound and provides information on the electronic structure of the analyte.

For most absorbing species Beer's law will only apply over a certain range, i.e. absorption will generally only be linear between 0.1 and 1. This is because in very dilute solutions small changes in concentration can result in large changes of transmittance, whereas at high con-centrations, the changes in the transmittance are very small.

Absorption spectrophotometry is potentially attractive for the semi-quantitative measurement of metal concentrations, as many of metal chloride complexes present in the leachate absorb in the UV range. The problem of deconvolution of the contributions from the different metal ion species to the spectral detected signal must be addressed. The preliminary results, Fig-ure 80, show that copper [II], iron [III], aluminium, zinc, nickel, lead[II], and tin [IV] metal chlor-ides absorb most strongly at different wavelengths, suggesting that deconvolution is feasible.



Figure 80 Absorption of metal chloride complexes

To provide calibration standards for future samples of unknown concentration and to enable further deconvolution of the received signal, the absorption spectra of the major metals present in EESs has been determined for a range of known concentrations (Table 17). To prevent their oxidation, solutions of CuCl, FeCl2, and SnCl2 were prepared in a glove bag in an inert (nitrogen) atmosphere, from de-oxygenated blank solution (4 M HCl and 1 M NaCl). Samples of the acidic metal chloride solution were placed in cuvettes of 1mm path length and analysed with a spectrophotometer. Examples of the results obtained are shown in Figure81 and Figure 82.

Table 17 Concentration Range for Absorption Samples.

Element Sample Concentration / mol m-3Copper 0, 1, 2, 3, 5, 10, 16.7, 25, 50

Iron 0, 1, 2, 3, 5, 10, 30

Aluminium 0, 10, 30

Tin 0,0.3, 0.5, 0.67, 1, 2, 3

Lead 0, 0.2, 0.25, 0.33, 0.5, 0.67, 0.75, 1

Nickel 0, 1, 2, 4, 8

Zinc 0,1,2,3,4



Figure 81 Absorption of lead chloride solution Figure 82 Absorption of iron chloride solution

The possibility of using a spectrophotometer follow the progress of the electrowinning pro-cess was demonstrated with the diluted solutions used during operation of the circulating par-ticulate bed reactor. The difference in the absorbance of the leachate solution initially and after 15 minutes when the majority of the copper has been depleted can be seen in Figure83. During these experiments it was found that determination of the aqueous chlorine con-centration would not be possible with spectrophotometry. Although chlorine does absorb in the UV region its contribution is dwarfed by the metal species.

Figure 83 Absorption of catholyte solution during electrowinning

The possibility of using a spectrophotometer to follow the progress of the leaching process can be seen from Figure 84 and Figure 85. This especially possible as the metals have been found to leach at different rates, and hence deconvolution of the received signal is usually only required for a few metals at one time.



Figure 84 Absorption of leachate solution containing 4.5 mol m-3 Fe (determined by ICP)

Figure 85: Absorption of leachate solution containing 1 mol m-3 Sn/Pb (determined by ICP)

During these experiments, taking samples was still necessary to measure the absorbance of species in the solutions, but was at least possible while the experiment was in progress. There is also potential for further improvements in comparison to the use of ICP, because the quartz cuvettes are available as flow-through cells for in-line analysis.

4.4.2.2 Amperometry

A literature review and preliminary investigations into the use of an amperometric sensor for an on-line semi-quantitative analysis of the leachate solution (ideally for both chlorine and metal concentrations) have been conducted.

The feasibility has been demonstrated of using the transport limited chlorine reduction cur-rent at a Pt rotating-disc electrode as the basis for a linear amperometric chlorine sensor. Levich’s equation predicts linear relationships between the transport controlled limiting cur-rent densities at a rotating disc electrode, the concentration of reactant (chlorine), and the square root of the rotation rate:



[4-10]

The results reported in Figure 86 show that reduction of chlorine (Cl2 + Cl3-) at a Pt rotating disc electrode exhibited mass transport controlled behaviour, in agreement with Levich’s equation [4-10] over the potential range 0.3-0.9 V (SHE).

Figure 86 Levich plot for 0.04 mol m-3 chlorine reduction in 3 kmol NaCl, 1 kmol HCl at 0.8 V (SHE).

It can also been seen in Figure 87 that for a synthetic leachate solution containing chlorine, gold, copper and tin, the mass transport controlled reduction of chlorine at a Pt rotating disc electrode, can form the basis of a linear amperometric sensor in the potential range 0.6-0.9 V (SHE), with minimal interference from metal ions such as Au(III), the most easily reduced metal species in the leach solutions.



Figure 87 Experimental current density – electrode potential data for reduction of the synthetic electrolyte at a Pt RDE rotating at 4 Hz.

4.4.2.3 In-line Measurements

The feasibility of spectrophotometric and amperometric sensors for process control have been demonstrated by the results obtained above. Hence a flow circuit, which can be seen in Figure 88 containing both microelectrode (for amperometry) and a quartz flow cell (for spectrophotometry), has been constructed to enable further development of an on-line sensor for process control.



Figure 88 Flow circuit containing microelectrode and quartz flow cell.

As the majority if the metals and chlorine absorb in the low UV region (less than 300nm) a new quartz fibre optic cable was required to transfer light to from the spectrophotometer to the quartz cell and back. Now that this has arrived from Germany, work has progressed for blank, chlorine and chlorine/single metal containing solutions. The spectrophotometric and amperometric results for chlorine are shown in Figure 89 and Figure 90 respectively.

Figure 89 Absorption of chlorine, HCl, NaCl



Figure 90 Experimental current density – electrode potential data for reduction of chlorine

In conclusion to this division of work, spectrophotometric and amperometric sensors for pro-cess control have been developed to enable on-line semi-quantitative measurement of the dissolved metal ion and chlorine concentrations.

4.4.3 Costs

Preliminary cost estimations for this process are given in this section. From the value of the recoverable metals present, the value of a typical printed circuit board is around 2931€/tonne. The average current efficiency for the electrowinning experiments performed to date has been greater than 90%, giving electrical energy costs of around 147€/tonne of boards processed. Even if, as expected, a compromise in efficiency must be made recovery the lead, zinc, nickel and iron, the costs are still extremely favourable, at less than 366€/tonne of shredded EESs.

More detailed costs for the process equipment, instruments, and running costs have also been estimated for a plant capable of processing 1 tonne per day of shredded electronics. Ten 100 kg/day leach column reactors, 1.6 m in height and 0.3 m in diameter, will be used to dissolve the metals from the WEEE. Fifteen electrochemical reactors, 1 m * 0.3 m * 0.1 m in size and with a circulating particulate bed cathode of area about 5 m2, will be required to re-cover the metal from solution. Power will be supplied by a 15 V, 3200 A transformer-rectifier. The equipment costs (including reactors, power supply, pumps, fittings, valves, instruments, pipe work, sensors, alarms, support frames, buns and reserviors) for a 1 tonne per day plant are approximately 161.196€. The assumption that the equipment costs constitute approxim-ately one quarter of the costs for the plant, buildings and services, gives a total capital ex-penditure to construct and install such a plant of less than 659.437€. Taking into account the expected lifetime for the different items of equipment, the total annual capital, operating and refining costs are below 175.850€, compared with an annual processed metal value of 732.708€.



4.5 Demonstration of the leaching-electrowinning reactor at Imperial College, London

The described lab scale leaching and electrowinning reactor for chemical recycling of pre-cious metals from granulated printed circuit boards (PCB) has been demonstrated during a public dissemination and demonstration event at Imperial College London on 25 April 2006. This event has been jointly organised with the UK WEEE-Tech project dealing with recycling of PCB from WEEE. The reactor has been developed at Imperial College London (subcon-tractor of RHEMEL) in a joint effort with partners from the WEEE-Tech project. About 30 per-sons, mainly from research and industry organisations, attended this event. The demonstra-tion event was hosted by Prof. Geoff Kelsall who has been the supervisor of the scientific activities at Imperial College for development of this reactor.

During the morning session there were presentations from invited speakers to introduce the backgrounds on the WEEE Directive, electronics processing and recycling, trends in material composition and an overview on the SEES project. Among the speakers were Kate Geraghty (RHEMEL) and André Greif (TUB) to represent the SEES project as well as industry repres-entatives from Sony and Sims Group. Kate Geraghty presented results from the analysed material composition of different kinds of PCB and outlined future trends in electronics. André Greif gave an introduction to the SEES project, its objectives and the SEES approach which provided the framework for the chemical recycling study.

The afternoon session consisted of a detailed presentation of the scientific and technical backgrounds on the developed leaching and electrowinning process by Prof. Kelsall and his colleagues. Afterwards the running reactor was demonstrated in the lab where physical samples of input material and treated PCB material were shown. It provided a good illustra-tion of the process capabilities to the audience.

Researchers at the department of Prof. Kelsall have been running the reactor for some weeks with different materials and setups to monitor and further optimise the process. This work will even continue after finishing the SEES WP4.

4.6 Conclusions

This report details the development and demonstration of chemical recycling techniques for the recovery of valuable and hazardous materials from end-of-life electronic devices, carried out by Rohm & Haas Electronic Materials Europe Ltd. together with its subcontractor Imperial College London as part of the SEES project.

Acidic aqueous chloride solutions containing chlorine have been determined as an appropri-ate (regenerable) oxidant for the recovery of metals from electronic scrap, while the work at Imperial College London has firmly established the feasibility of using chlorine in a chlorine leach-electrowin process for the treatment of waste electronic material.

The operating leaching conditions are suggested as at least 5 M chloride ions, a pH of less than zero, and 100 mol m-3 dissolved chlorine concentration, to drive the dissolution of the metals from the electronic scrap. As discussed above, it is proposed that a packed bed re-actor operating in continual mode is likely to yield the best performance for the leaching of metals from EESs. Hence this is the type of reactor which is being designed and on which further experiments are being performed. Given that the dissolution reactions are limited by the chlorine gas concentration, it is expected that co-current downflow packed bed (trickle



bed) reactor is the best flow arrangement. From considering the effect of mechanical shred-ding processes on subsequent chemical extraction efficiencies, it is expected that splitting the mechanically treated EESs into two, and leaching the smaller particles in an agitated re-actor and the larger ones in a packed column may be the most cost efficient option.

For the recovery of metals from solution, it has been found that semi-selective electrowinning at a variety of potentials (e.g. V1 = -0.5 V, V2 = -0.7 V) is the most efficient method of metal recovery. It has also been shown by exhaustive electrolysis that complete recovery of cop-per, silver, gold and palladium is possible from the leachate solution in about six hours, at po-tentials below -0.4 V (SCE), with a high current efficiency. The potential can then be stepped down to below -0.6 V (SCE), for essentially complete removal of the tin and lead within a fur-ther three hours (also at high current efficiency as both metals are poor catalysts for the evol-ution of hydrogen). During the electrowinning experiments, approximately 20% of the zinc, iron, and nickel deposited as a result of alloy formations, catalysing hydrogen evolution and decreasing current efficiencies. No depletion of the aluminium concentration was measured during exhaustive electrolysis, as it is not possible to reduce it from aqueous solutions.

5 Application of SEES Evaluation Methodologies to six EES Products

5.1 Introduction

Two new methodologies have been developed in the WP7 of the SEES Project (see SEES Deliverable D7) to quantify the recyclability and recoverability potential of EES products and to simulate end-of-life scenarios. These two methodologies have been ap-plied to the following six EES products:

Passive Junction Box (PJB) passenger compartment -

Seat mechatronic

Passenger Smart Junction Box (PSJB)

Wire harness engine compartment -

Alternator

Lambda sensor (exhaust gas)

The main results and conclusions of these six case studies are presented in this chapter.

It is important to mention that the main purpose of these six case studies was the testing and the validation of the two methodologies based on current product designs and current disas-sembly processes (mostly manual) and the studied recycling technologies. Therefore, con-clusions of case studies should not be considered as general conclusions & recommenda-tions applicable to these or other EES.

5.2 Summary of the two Developed Methodologies

This section presents a summary of the two developed methodologies:

i) methodology for quantifying recyclability and recoverability potential of EES



ii) methodology for simulating end-of-life scenarios of EES

These methodologies are described in the public report of the SEES project D7: Economical and Environmental Assessment, which can be downloaded at www.sees-project.net.

With this tandem of methodologies, balances between “disassembly efforts” vs. the corres-ponding “end-of-life consequences” can be performed for assessing the appropriateness or expected end-of-life results due to disassembly operations.

The two developed methodologies are currently implemented in software tools within the SEES Project.

5.2.1 Recyclability and Recoverability Potential of EES (Methodology 1)

This is a quantitative methodology for assessing recyclability, re-usability and recoverability potential of current and new designs of automotive Electrical and Electronic Systems (EES). The need, value and effort of destructive or non-destructive dismantling of an EES product or parts of it are assessed in this methodology considering their composition and other specific design parameters. This enables more objective and practical comparisons of alternative EES designs. Application of this methodology supports design for dismantling, re-use, recyc-ling and recovery of EES products.

The six main calculation steps of this methodology are described in this section.

STEP 1: Product characterisation

For characterising the product under study, the following info is pre-required:

number and name of components or parts of the target product

structure of the target product parts and connections between them -

weight of components or parts of the target product

detailed composition of the target product and its parts

“prohibited” and “declarable” substances according to the GADSL list

STEP 2: Recyclability & recoverability potential ISO 22628

This calculation step is integrated by the three following calculation sub-steps.

SUB-STEP 2.1: Recyclability and recoverability rates

It is a simple adaptation of the ISO 22628:2002 method for calculating recyclability and re-coverability rates of automotive EES products based on their weight and composition which can be potentially recycled and recovered.

The user should indicate if the product or its parts have a “potential market for re-use” and the methodology calculates the corresponding recyclability and recoverability rates by con-sidering their weight, composition and proposed recyclability and recoverability percentages of recycling technologies.



SUB-STEP 2.2: Transformation of mass indicators into costs indicators

The previous mass rates are transformed into costs indicators by considering the market price of recyclable material flows and re-usable components and depending on recycling, re-covery or disposal technologies.

Proposed (-) recycling benefits or (+) disposal costs (London Metal Exchange, year 2005):

Ferrous metals (iron, steel, etc.): - 0.14 €/kg

Unknown non-ferrous metals: - 0.14 €/kg

Aluminium (Al): - 1.309 €/kg

Copper (Cu): - 3.148 €/kg

Lead (Pb): - 0.761 €/kg

Tin (Sn): - 5.533 €/kg

Silver (Ag): - 187 €/kg

Polypropylene (PP): - 1.57 €/kg

Disposal cost: + 0.1 €/kg

SUB-STEP 2.3: Proven recycling technologies

Besides mass and costs indicators, some information about available proven recycling and recovery technologies for the analysed EES product is another output.

STEP 3: Necessity of a first level disassembly

In this step, the user should decide about the necessity or appropriateness of a first level dis-assembly step, or in other words, to extract the EES from the vehicle. This decision can be supported or motivated by several reasons and criteria. In this methodology is obligatory to consider, at least, the three following criteria: 1) legal duty to dismantle, 2) potential economic end-of-life value for re-use and 3) content of heavy metals mentioned at the ELV Directive.

The methodology includes a table with a qualitative A/B/C assessment of the most common automotive EES components in the three mentioned criteria. In each criteria the value “A” is given for highest relevance of component whereas “C” represents low relevance of compon-ent in that criteria (for example for heavy metals: A = high (x > 5 g), B = middle (1 g < x < 5 g) and C = low (x < 1 g)).

The user should select A, B or C in each of the obligatory three criteria for the whole product and for each component part. Based on this assessment, the methodology will guide the user to a decision whether to consider disassembly or not for the whole product and for each com-ponent part. The four possible answers of this assessment are the following: 1) disassembly necessary, 2) recommended, 3) not recommended or 4) no clear recommendation. Finally, the total content of heavy metals mentioned in the ELV Directive (Pb, Hg, Cd and Cr+6) is cal-culated for the whole product and for each component part.



STEP 4: First level disassembly

If a first level disassembly step is chosen or required, the user of the methodology should provide some extra data and information for quantifying the “effort” of extracting the target product from the vehicle.

The user should assign an identification number to each fastener, of the target product and of any previous part to be removed, and then (per each individual fastener) the following inform-ation should be provided:

coordinates and location (x, y, z) for knowing its relative position

type of fastener (selection from a closed list)

priority (order or level in which fasteners should be disassembled)

accessibility, visibility and corrosion of fasteners (selection from a closed list)

taking-off/breaking direction (selection from a closed list)

With all previous information, the following design indicators are calculated:

total number of fasteners

different types of fasteners (for knowing variability and tooling)

dominant accessibility of fasteners

dominant taking-off/breaking direction

number of different tools required

distances between fasteners (transitions in xy, xz and yz)

suggested best disassembly sequence

These previous indicators are transformed into estimated disassembly times and costs by us-ing default values for the desired disassembly sequence (default cost of 1h is 40 €):

type and quantity of fasteners

accessibility, visibility and corrosion of fasteners

tool changing (due to type and quantity of fasteners)

changes in taking-off/breaking direction

transitions between fasteners

TOTAL estimated disassembly time

STEP 5: Necessity of a second level disassembly

In this step the user should decide about the necessity or appropriateness of a second level disassembly step, or in other words, to disassemble the EES into its different component parts and materials. Again, this decision can be motivated by several reasons (e.g. easier re-cycling or recovering, more economic benefits, re-usability of component parts, etc.). The tool includes some key questions to guide the user to the right decision, for example:



are hazardous substances concentrated in a part of the product?

are valuable materials concentrated in a part of the product?

are possible recycling contaminants concentrated in a part of the product?

are single parts of the product of high value for re-use?

STEP 6: Second level disassembly

Analogously to the first level disassembly step, if a second level disassembly step is chosen, the user should provide some extra data for quantifying the “effort” of disassembling the tar-get product into its component parts. Information requirements, calculated design indicators and estimated disassembly times & costs are analogous to those presented in step 4 (first level disassembly).

Finally, the methodology can also calculate “aggregated indicators” or the corresponding “design indicators” and the “estimated disassembly times” due to step 4 (first level disas-sembly) and step 6 (second level disassembly).

5.2.2 End-of-life Scenarios of EES (Methodology 2)

In this second methodology, the users use a simple interface in which they only have to intro-duce the input material of the EES part or material flow to be assessed, with the same format used in the first methodology, and to select the desired and available end-of-life process or a sequence of them -, for simulating the EES mass, economical and environmental con-sequences.

The user has to choose processes considering their applicability and restrictions to the product under assessment. The following three processes are available for chemical and mechanical recycling of EES:

Mechanical recycling of junction boxes

Mechanical recycling of wire harnesses

Chemical recycling of PCBs

Additionally, the user also has the opportunity of checking, adapting or modifying the pro-posed default data and/or functions of the reproduced processes (optional).

The application of this methodology provides the following input and output indicators:

INPUT INDICATORS (a detailed and an aggregated list is provided within each category)

Input material (in kg and in €)

Additional material/fuels (in kg and €)

Electricity (in kWh and in €)

Heat (in MJ and in €)

Personnel (in h and in €)

Machinery (in h and in €)



Transport (in km and in €)

Sub-total costs of inputs (in €)

OUTPUT INDICATORS (a detailed and an aggregated list is provided within each category)

Waste to treatment (in kg and in €)

Emissions to air (in kg)

Emissions to water (in kg)

Emissions to soil (in kg)

Non-material emissions (in kg)

Supplementary costs (in €)

Recyclable material (in kg and in €)

Sub-total costs of outputs (in €)

Total costs of inputs + outputs (in €)

5.3 Main Results and Conclusions of the 6 Case Studies

In this section, the main results and conclusions of the application of the two developed methodologies (quantification of recyclability and recoverability potential and simulation of end-of-life scenarios of EES) to the following six different EES products are presented:

Passive Junction Box (PJB) passenger compartment -

Seat mechatronic

Passenger Smart Junction Box (PSJB)

Wire harness engine compartment -

Alternator

Lambda sensor (exhaust gas)

In each case study, the first part presents the main results and conclusions of the assess-ment of the recyclability and recoverability potential of the EES product (Methodology 1) and the second part presents the main results and conclusions of considering some alternative end-of-life scenarios instead of a manual 2nd level disassembly (Methodology 2).

It is important to mention again that the main purpose of these six case studies was the test-ing and the validation of the methodologies based on current designs of specific products and current disassembly processes (mostly manual). Therefore, conclusions of case studies should not be considered as general conclusions & recommendations applicable to these or other EES.

5.3.1 Passive Junction Box (PJB) Passenger Compartment -

5.3.1.1 Assessment of Recyclability and Recoverability Potential




Figure 91. Example of Passive Junction Box (PJB)

Table 18. Characterisation of Passive Junction Box

Target product PJB

Total weight (g) 880.44

Number of main parts 3

COMPOSITION (g) MATERIAL403.84 Cu

306.50 PP

150.00 Epoxi resin

10.27 Sn

6.03 Pb

3.80 Unknown ferrous metals

The PCB of the box contains 404 g of Cu (the solder is SnPb)Part 1:

Name Housing

Weight (g) 192.00

COMPOSITION (g)

192.00 PP



Part 2:

Name Connectors housing

Weight (g) 114.50

COMPOSITION (g)

114.50 PP

Part 3:

Name PCB

Weight (g) 573.94

COMPOSITION (g)

403.84 Cu

150.00 Epoxi resin

10.27 Sn

6.03 Pb

3.80 Unknown ferrous metals

The PCB contains 404 g of Cu (the solder is SnPb)

STEP 2: Recyclability & recoverability potential ISO 22628The whole product:

Name PJB

Weight (g) 880.44

g % weight €

Reusable 0 0 0

Recyclable 880.44 100 -1.81

Energy recovery 0 0 0

Disposal 0 0 0

TOTAL 880.44 100 -1.81

Recyclability (%) 100

Recoverability (%) 100

This product has a limited market for being reused



The total potential benefit of recycling is approximately 1.81 € per box

Part 1:

Name Housing

Weight (g) 192.00

g % weight €Reusable 0 0 0

Recyclable 192.00 100 -0.30


Disposal 0 0 0

TOTAL 192.44 100 -0.30



The housing (PP) represents 17% of the total potential benefit of recycling a box

Part 2:


Weight (g) 114.50


Recyclable 114.50 100 -0.18


Disposal 0 0 0

TOTAL 114.50 100 -0.18



Connectors housing (PP) represents 10% of total potential benefit of recycling a box

Part 3:

Name PCB

Weight (g) 573.94




Recyclable 573.94 100 -1.33


Disposal 0 0 0

TOTAL 573.94 100 -1.33



The PCB represents 73% of the total potential benefit of recycling a box


The whole product:

Name PJB

Legal duty to dismantle B

Economic end-of-life value for reuse B

Content of heavy metals (ELV Directive) A

RECOMMENDATION Disassembly recommended

Lead (g) 6.031

Mercury (g) 0

Cadmium (g) 0

Hexavalent chromium (g) 0

TOTAL (g) 6.031

Disassembly would be only recommended if overall Pb in solder in total vehicle is > 60 g

Disassembly could be justified due to the content of 6.031 g of Pb in the PCB

The SnPb (solder) will be lost during the shredding process if the box is not extracted

The 404 g of Cu of the PCB implies a potential economic end-of-life value for recycling



Part 1:

Name Housing

Legal duty to dismantle C

Economic end-of-life value for reuse C

Content of heavy metals (ELV Directive) C

RECOMMENDATION Disassembly not recommended

Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0

Disassembly is not recommended for this part

Part 2:






Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0




Part 3:

Name PCB





Lead (g) 6.031

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 6.031



The SnPb (solder) will be lost during the shredding process if the PCB is not extracted



Name PJB

Previous parts Target product TOTALNumber of fasteners (u) 8 4 12

Types of fasteners (u) 2 3 4

Previous parts Target product TOTALmin avg max min avg max min avg max

Estimated disassembly time (s)

39 77 153 86 121 162 124 198 315

Estimated disassembly cost (€) 0.43 0.86 1.70 0.96 1.34 1.80 1.38 2.20 3.50

The estimated average disassembly time is 198 seconds (77 seconds for previous parts)

The estimated average disassembly cost is 2.20 € (0.86 € for previous parts)



The estimated disassembly cost is 1.22 times the total potential benefit of recycling a box




The whole product:

Name PJB

Are hazardous substances in the assessed part? Yes

Are valuable materials in the assessed part? Yes

Are possible recycling contaminants in the assessed part? No

Is the assessed part of high value for re-use? No

The PCB contains 6.031 g of Pb


Part 1:

Name Housing

Are hazardous substances in the assessed part? No

Are valuable materials in the assessed part? No



The disassembly of this part might be necessary if the PCB needs to be dismantled

Part 2:







Part 3:

NamePCB

Are hazardous substances in the assessed part?Yes


Are possible recycling contaminants in the assessed part?No

Is the assessed part of high value for re-use?No



The PCB contains 6.031 g of Pb



Name PJB

Number of fasteners (u) 5

Types of fasteners (u) 4

min avg max


136 221 338

Estimated disassembly cost (€) 1.51 2.46 3.76

The estimated average disassembly time is 221 seconds

The estimated average disassembly cost is 2.46 €

The disassembly cost is 1.36 times higher than the total potential benefit of recycling a box

Aggregated indicators (1st + 2nd level disassembly)

Name PJB



min avg max


260 419 652


The total estimated average disassembly time is 419 seconds

The total estimated average disassembly cost is 4.66 €

The total disassembly cost is 2.57 times higher than the total benefit of recycling a box

Final comments and conclusions of the assessment:






The 404 g Cu (PCB) implies an economic value for recycling (unviable, see below)

For reaching the PCB (Pb & Cu), the box would need to be extracted and opened

The overall disassembly process is unviable (2.57 times the total potential benefit)

These processes and the design of the product requires optimisation for being viable

In the studied conditions, the disassembly of the PJB is not recommended

5.3.1.2 Assessment of Alternative End-of-life Scenarios

In that case, the following alternative scenario has been assessed with the 2nd methodology:

1st level disassembly,

mechanical recycling of boxes,

chemical recycling of PCBs, and

recycling of PP.

The main results and conclusions of this alternative scenario are presented hereafter:





For reaching the PCB (Pb & Cu), the box would need to be extracted and opened


Instead of a manual 2nd level disassembly, the mechanical recycling of the box is stud-ied

The mechanical recycling of the box implies a cost of approximately 0.03 € per box

The chemical recycling of the PCB implies a benefit of approximately 1.31 € per box

Additionally, an extra benefit of 0.48 € per box is assumed for plastic parts of PP

The overall disassembly and recycling process is unviable (0.44 € per box)

This strategy is better than a manual 2nd disassembly process (6.5 times cheaper)

In the studied conditions, the disassembly of the PJB is not recommended



5.3.2 Seat Mechatronic



The whole product:

Figure 92. Example of seat mechatronic unit

Table 19. Characterisation of seat mechatronic unit

Target product Seat mechatronic



COMPOSITION (g)97.70 ABS

46.48 Cu

40.84 Epoxi resin

32.39 Unknown metals

25.32 Unknown others

13.53 Unknown polymers

2.25 Sn

1.32 Pb

0.10 Polymer composite

0.04 Ag

The PCB of the box contains 46 g of Cu (the solder is SnPb)

The PCB contains precious metals (the exact amount is unknown)

The box contains 98 g of ABS



Part 1:

Name Connectors cover

Weight (g) 4.90

COMPOSITION (g)

4.90 ABS

Part 2:

Name Front cover

Weight (g) 7.90

COMPOSITION (g)

7.90 ABS

Part 3:

Name Lower cover

Weight (g) 42.90

COMPOSITION (g)

42.90 ABS

Part 4:

Name Top cover

Weight (g) 42.00

COMPOSITION (g)

42.00 ABS

Part 5:

Name Label PCB

Weight (g) 0.03

COMPOSITION (g)



Part 6:

Name Label product final

Weight (g) 0.08

COMPOSITION (g)


Part 7:

Name Circuit

Weight (g) 162.18

COMPOSITION (g)

46.48 Cu

40.84 Epoxi resin




2.25 Sn

1.32 Pb

0.04 Ag

The PCB contains 46 g Cu (solder SnPb) and precious metals (exact amount unknown)


The whole product:

Name Seat mechatronicWeight (g) 259.99


Recyclable 234.66 90 -0.165


Disposal 25.32 10 0.003

TOTAL 259.99 100 -0.162





The total potential benefit of recycling is only approximately 0.162 € per box


This product has some markets for being reused

Part 1:


Weight (g) 4.90


Recyclable 4.90 100 0


Disposal 0 0 0

TOTAL 4.90 100 0



Part 2:

Name Front cover

Weight (g) 7.90


Recyclable 790 100 0


Disposal 0 0 0

TOTAL 790 100 0





Part 3:

Name Lower cover

Weight (g) 42.90




Disposal 0 0 0

TOTAL 42.90 100 0



Part 4:

Name Top cover

Weight (g) 42.00




Disposal 0 0 0

TOTAL 42.00 100 0



Part 5:

Name Label PCB

Weight (g) 0.03

g % weight €



Reusable 0 0 0



Disposal 0 0 0

TOTAL 0.03 100 0



Part 6:


Weight (g)




Disposal 0 0 0

TOTAL 0.08 100 0



Part 7:

Name Circuit

Weight (g) 162.18


Recyclable 136.86 84 -0.165


Disposal 25.32 16 0.003

TOTAL 162.18 100 -0.162





The total potential benefit of recycling is approximately 0.162 € per PCB



The whole product:

Name Seat mechatronic




RECOMMENDATION No clear recommendation

Lead (g) 1.323

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 1.323

No clear recommendation about the necessity of disassembling this component

In favour of disassembling:

- The PCB contains precious metals (the exact amount is unknown)

- This product has some markets for being reused

Against disassembling:

- The content of Pb is only 1.323 g in the PCB

- The PCB only contains 46 g of Cu

- The total potential benefit of recycling a box is only approximately 0.162 €

Part 1:








Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 2:

Name Front cover





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 3:

Name Lower cover







Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 4:

Name Top cover





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 5:

Name Label PCB





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0




TOTAL (g) 0


Part 6:






Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 7:

Name Circuit





Lead (g) 1.323

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 1.323

No clear recommendation can be given about the necessity of disassembling the PCB

In favour of disassembling:




Against disassembling:



- The total potential benefit of recycling the PCB is only approximately 0.162 €







400 600 800 10 19 38 410 619 838


The estimated average disassembly time is 619 seconds (600 s for previous parts)


The estimated disassembly cost is 42 times the total potential benefit of recycling the box


The whole product:






The content of Pb is only 1.323 g in the PCB

The PCB only contains 46 g of Cu


Part 1:









Part 2:

Name Front cover






Part 3:

Name Lower cover






Part 4:

Name Top cover








Part 5:

Name Label PCB





The disassembly of this part is unnecessary

Part 6:






The disassembly of this part is unnecessary

Part 7:

Name Circuit





The content of Pb is only 1.323 g in the PCB

The PCB only contains 46 g of Cu








min avg max


19 23 26




The estimated disassembly cost is 1.60 times higher than the total benefit of recycling a box





min avg max


429 642 864




The estimated disassembly cost is 44 times higher than the total benefit of recycling a box


In favour of disassembling the component:



Against disassembling the component:




Pb, Cu and precious metals are in the PCB

For reaching the PCB, the box would need to be extracted from the vehicle and opened

The overall disassembly process is unviable (44 times the potential benefit)


In the studied conditions, the disassembly of seat mechatronic is not recommended




In that case, the following alternative scenario has been assessed with the 2nd methodology:


mechanical recycling of boxes, and

chemical recycling of PCBs.


In favour of disassembling the component:



Against disassembling the component:




Pb, Cu and precious metals are in the PCB

For reaching the PCB, the box would need to be extracted from the vehicle and opened




The chemical recycling of the PCB implies a benefit of approximately 0.51 € per box

The overall disassembly and recycling process is unviable (6.38 € per box)

In the studied conditions, the disassembly of seat mechatronic is not recommended

5.3.3 Passenger Smart Junction Box (PSJB)



The whole product:



Figure 93. Example of PSJB

Table 20. Characterisation of PSJB

Target product PSJB

Total weight (g) 1,327.86


COMPOSITION (g)

462.00 PP

228.93 Epoxi resin

194.60 Unknown non-ferrous metals


133.67 Cu



29.36 Sn

13.30 Pb

0.24 Ag

The 3 PCBs of the box contain 134 g of Cu (the solder is SnPb)

The electronic PCB contains precious metals (the exact amount is unknown)

The box contains 462 g of PP

Part 1:

Name Fuse cover

Weight (g) 243.40

COMPOSITION (g)

243.40 PP

Part 2:

Name Electronic & quick cover

Weight (g) 182.60



(g)

182.60 PP

Part 3:

Name Isolator

Weight (g) 36.00

COMPOSITION (g)

36.00 PP

Part 4:

Name Power PCB1

Weight (g) 551.22

COMPOSITION (g)


124.80 Epoxi resin


83.20 Cu


19.03 Sn

8.32 Pb

7.30 Unknown others

0.18 Ag

The power PCB1 contains 83 g of Cu (the solder is SnPb)Part 5:

Name Power PCB2

Weight (g) 184.38

COMPOSITION (g)

46.68 Epoxi resin


31.32 Cu



7.04 Sn



3.08 Pb

2.70 Unknown others

0.07 Ag

The power PCB2 contains 31 g of Cu (the solder is SnPb)



Part 6:

Name Electronic PCB

Weight (g) 130.26

COMPOSITION (g)

57.45 Epoxi resin


19.15 Cu

3.30 Sn

1.90 Pb

The electronic PCB contains 19 g of Cu (the solder is SnPb)



The whole product:

Name PSJB

Weight (g) 1,327.86


Recyclable 1,269.40 96 -1.66


Disposal 58.46 4 0.006

TOTAL 1,327.86 100 -1.65



The total potential benefit of recycling is approximately 1.65 € per box

The 3 PCBs represent the 66% of the total potential benefit of recycling a box

The PP parts represent the 44% of the total potential benefit of recycling a box

This product has some markets for being reused



Part 1:

Name Fuse cover

Weight (g) 243.40


Recyclable 243.40 100 -0.38


Disposal 0 0 0

TOTAL 243.40 100 -0.38



The fuse cover (PP) represents 23% of the total potential benefit of recycling a box

Part 2:


Weight (g) 182.60


Recyclable 182.60 100 -0.29


Disposal 0 0 0

TOTAL 182.60 100 -0.29



The electronic & quick cover (PP) represents 18% of total benefit of recycling a box

Part 3:

Name Isolator

Weight (g) 36.00




Recyclable 36.00 100 -0.06


Disposal 0 0 0

TOTAL 36.00 100 -0.06



The isolator (PP) represents 4% of the total potential benefit of recycling a box

Part 4:

Name Power PCB1

Weight (g) 551.22


Recyclable 543.92 99 -0.64


Disposal 7.30 1 0.001

TOTAL 551.22 100 -0.64



The power PCB1 represents 39% of the total potential benefit of recycling a box

Part 5:

Name Power PCB2

Weight (g) 184.38


Recyclable 181.68 99 -0.21




Disposal 2.70 1 0.0003

TOTAL 184.38 100 -0.21



The power PCB2 represents 13% of the total potential benefit of recycling a box

Part 6:

Name Electronic PCB

Weight (g) 130.26

g % weight €

Reusable 0 0 0

Recyclable 81.80 63 -0.08


Disposal 48.46 37 0.005

TOTAL 130.26 100 -0.08



The electronic PCB represents 5% of the total potential benefit of recycling a box


The whole product:

Name PSJB







Lead (g) 13.296

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 13.296


Disassembly could be justified due to the content of 13.296 g of Pb in the 3 PCBs


Additionally:

-The 134 g of Cu in the 3 PCB implies a potential economic end-of-life value for recycling

-The 462 g of PP of plastic parts implies a potential economic value for recycling

-The electronic PCB contains precious metals (the exact amount is unknown)

-This product has some markets for being reused

Part 1:

Name Fuse cover





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 2:








Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 3:

Name Isolator





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 4:

Name Power PCB1







Lead (g) 8.320

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 8.320





Part 5:

Name Power PCB2



Content of heavy metals (ELV Directive) B


Lead (g) 3.076

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 3.076

No clear recommendation for this part

This PCB contains 3.076 g of Pb


This PCB contains 31 g of Cu

Part 6:

Name Electronic PCB







Lead (g) 1.900

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 1.900





This PCB contains precious metals (the exact amount is unknown)


Name PSJB





5 9 16 20 36 67 25 45 82




The estimated disassembly cost is 0.30 times the total potential benefit of recycling the box


The whole product:

Name PSJB







The 3 PCBs contain 13.296 g of Pb

The 134 g of Cu in the 3 PCB implies a potential economic end-of-life value for recycling

The 462 g of PP of plastic parts implies a potential economic end-of-life value for recycling


Part 1:

Name Fuse cover





The disassembly of this part might be necessary if PCBs need to be dismantled

Additionally, PP implies a potential economic end-of-life value for recycling

Part 2:








Part 3:

Name Isolator







Part 4:

Name Power PCB1







Part 5:

Name Power PCB2







Part 6:

Name Electronic PCB







This PCB contains precious metals (the exact amount is unknown)




Name PSJB



min avg max


84 165 324




The disassembly cost is 1.11 times higher than the total potential benefit of recycling a box


Name PSJB



min avg max


109 211 406




The total disassembly cost is 1.42 times higher than the total benefit of recycling a box





Additionally:

- The 134 g of Cu in the 3 PCB implies a potential economic end-of-life value for recycling



- The 462 g of PP of plastic parts implies a potential economic value for recycling

- The electronic PCB contains precious metals (the exact amount is unknown)




Pb & Cu in the 3 PCBs. For reaching the PCBs, the box should be extracted and opened

Precious metals are in the electronic PCB. The box should be extracted and opened

The 1st disassembly process is economically viable (0.30 times the total potential bene-fit)



In the studied conditions, the disassembly of a PSJB is not recommended


That case, the following alternative scenario has been assessed with the 2nd methodology:


mechanical recycling of boxes,

chemical recycling of PCBs, and

recycling of PP.





Additionally:

- The 134 g of Cu in the 3 PCB implies a potential economic end-of-life value for recycling

- The 462 g of PP of plastic parts implies a potential economic value for recycling

- The electronic PCB contains precious metals (the exact amount is unknown)


Pb & Cu in the 3 PCBs. For reaching the PCBs, the box should be extracted and opened

Precious metals are in the electronic PCB. The box should be extracted and opened




The chemical recycling of the 3 PCBs implies a benefit of approximately 2.25 € per box

Additionally, an extra benefit of 0.73 € per box is assumed for plastic parts of PP

The overall disassembly & recycling process is viable (benefit = 2.43 €/box)

In the studied conditions, the disassembly of the PSJB could be justified



5.3.4 Wire Harness Engine Compartment



Figure 94. Example of wire harness - engine compartment -

Table 21. Characterisation of wire harness

Target product Wire harness



COMPOSITION (g)2,476.26 Cu

940.92 PP

871.42 PVC

222.75 PA

The wire harness contains 2,476 g of Cu and other plastics that can be recovered




Name Wire harness

Weight (g) 5,862.20


Recyclable 5,862.20 100 -9.272


Disposal 0 0 0

TOTAL 5,862.20 100 -9.272



The total benefit of recycling the Cu and the plastics is approximately 9.27 €


Name Wire harness





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0

Disassembly of wire harness is not required as long as the content of Cu has no eco-nomic net end-of-life value (see below). The value “A” in content of heavy metals is related to lead in battery cable terminals and seems properly to dismantle them together with the battery.




Name Wire harness





0 0 0 600 1,200 1,800 600 1,200 1,800


The estimated average disassembly time is 1,200 seconds


The disassembly cost is 1.44 times the total potential benefit of recycling the wire har-ness


Name Wire harness



Are possible recycling contaminants in the assessed part? Yes


A second level disassembly is not required


Cu (2,476 g of Cu) implies a potential economic end-of-life value (unviable, see below)

The total potential benefit of recycling the Cu and the plastics is approximately 9.27 €

The extraction of the wire harness from the ELV is unviable (13.33 € per wire harness)

The disassembly cost is 1.44 times the total potential benefit of recycling the wire har-ness

The extraction process and design of the wire require optimisation for being viable



The overall disassembly and recycling process is unviable (4.06 €/wire harness)

In the studied conditions, the disassembly of wire harness is not recommended




In the SEES Project the mechanical recycling of wire harness has been studied: chopping, shredding and separating of wire harness constituents. The mechanical recycling of wire har-ness implies a benefit of 1.32 € per wire harness (without considering disassembly costs).


Cu (2,476 g of Cu) implies a potential economic end-of-life value (unviable, see below)

The extraction of the wire harness from the ELV is unviable (13.33 € per wire harness)

The mech. recycling of wire harness implies only a benefit of 1.32 € per wire harness

The extraction process and design of the wire require optimisation for being viable

The overall disassembly and recycling process is unviable (12.01 €/wire harness)

In the studied conditions, the disassembly of wire harness is not recommended

5.3.5 Alternator



The whole product:

Figure 95. Example of alternator



Table 22. Characterisation of alternator

Target product Alternator



COMPOSITION (g)

2,096.64 Iron

1,026.83 Cu

1,011.17 Al

601.96 Steel

240.70 PA

8.00 Polyester

2.00 Pb

It contains important amounts of metals that can be recovered (iron, Cu, Al & steel)

The alternator contains 2 g of Pb in brushes (source: Heavy Metals in Vehicles II, Öko-pol). This source is now out-dated as all vehicles comply to new Annex II of Directive 2000/53/EC

Part 1:

Name Stator

Weight (g) 1,075.30

COMPOSITION (g)

713.53 Iron

356.77 Cu

5.00 PA

Part 2:

Name Rotor shaft + coil

Weight (g) 1,897.00

COMPOSITION (g)

843.11 Iron

632.33 Cu

421.56 Steel



Part 3:

Name Rectifier

Weight (g) 162.30

COMPOSITION (g)

90.17 Al

54.10 PA

18.03 Cu

Part 4:

Name Rear & front housing

Weight (g) 994.00

COMPOSITION (g)

921.00 Al

73.00 PA

Part 5:

Name Bearings

Weight (g) 122.40

COMPOSITION (g)

122.40 Steel

Part 6:

Name Fasteners

Weight (g) 152.20

COMPOSITION (g)

112.50 Iron

39.70 Steel



Part 7:

Name Others

Weight (g) 584.10

COMPOSITION (g)

427.50 Iron

108.60 PA

19.70 Cu

18.30 Steel

8.00 Polyester

2.00 Pb



The whole product:

Name Alternator

Weight (g) 4,987.30


Recyclable 4,987.30 100 -6.305


Disposal 0 0 0

TOTAL 4,987.30 100 -6.305



This product has an acceptable market for being reused

The total potential benefit of recycling is approximately 6.31 € per alternator



Part 1:

Name Stator

Weight (g) 1,075.30


Recyclable 1,075.30 100 2.446


Disposal 0 0 0

TOTAL 1,075.30 100 -2.446



This part represents 39% of the total potential benefit of recycling an alternator

Part 2:


Weight (g) 1,897.00


Recyclable 1,897.00 100 -2.167


Disposal 0 0 0

TOTAL 1,897.00 100 -2.167




Part 3:

Name Rectifier

Weight (g) 162.30




Recyclable 162.30 100 -0.187


Disposal 0 0 0

TOTAL 162.30 100 -0.187




Part 4:


Weight (g) 994.00


Recyclable 994.00 100 -1.334


Disposal 0 0 0

TOTAL 994.00 100 -1.334




Part 5:

Name Bearings

Weight (g) 122.40


Recyclable 122.40 100 -0.017


Disposal 0 0 0



TOTAL 122.40 100 -0.017



This part represents 0.3% of the total potential benefit of recycling an alternator

Part 6:

Name Fasteners

Weight (g) 152.20


Recyclable 152.20 100 -0.021


Disposal 0 0 0

TOTAL 152.20 100 -0.021



This part represents 0.3% of the total potential benefit of recycling an alternator

Part 7:

Name Others

Weight (g) 584.10


Recyclable 584.10 100 -0.132


Disposal 0 0 0

TOTAL 584.10 100 -0.132





This fraction represents 2% of the total potential benefit of recycling an alternator


The whole product:

Name Alternator


Economic end-of-life value for reuse A



Lead (g) 2.000

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 2.000

Disassembly could be recommended due to potential market to reuse

Part 1:

Name Stator





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0




Part 2:






Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 3:

Name Rectifier





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 4:








Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 5:

Name Bearings





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0


Part 6:

Name Fasteners





Lead (g) 0

Mercury (g) 0



Cadmium (g) 0


TOTAL (g) 0


Part 7:

Name Others





Lead (g) 2.000

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 2.000



Name Alternator





0 0 0 226 441 562 226 441 562

Estimated disassembly cost (€) 0 0 0 2.51 4.89 6.24 2.51 4.89 6.24





The disassembly cost is 0.77 times the total potential benefit of recycling the alternator




The whole product:

Name Alternator





It contains important amounts of metals that can be recovered (iron, Cu, Al and steel)


Part 1:

Name Stator





Part 2:






Part 3:

Name Rectifier






Part 4:






Part 5:

Name Bearings





Part 6:

Name Fasteners





Part 7:

Name Others








Name Alternator



min avg max


134 260 435




The disassembly cost is 0.46 times the total potential benefit of recycling an alternator


Name Alternator



min avg max


360 701 987

Estimated disassembly cost (€) 4,00 7.78 10.96



The total disassembly cost is 1.23 times higher than the benefit of recycling an alternator


Disassembly could be recommended due to potential market to reuse

The disassembly process is economically unviable (1.23 times the total benefit)


In the studied conditions, the disassembly of an alternator is recommended for reusing purposes and not recommended for recycling or depollution (Pb) purposes.



5.3.6 Lambda Sensor (exhaust gas)



Figure 96. Example of lambda sensor

Table 23. Characterisation of lambda sensor

Target product Lambda Sensor



COMPOSITION (g)

34.90 gUnknown ferrous metals

23.20 gCeramics + metals (Pt + Pd)

8.50 gUnknown metals

3.40 gUnknown thermosets

3.20 gUnknown others

The sensor contains 41 mg Pt and 21 mg Pd precious metals -




Name Lambda Sensor

Weight (g) 73.20


Recyclable 46.80 64 1.003


Disposal 26.40 36 0.003

TOTAL 73.20 100 1.00



The total value of precious metals (41 mg Pt + 21 mg Pd) is approximately 1 € per sensor


Name Lambda Sensor





Lead (g) 0

Mercury (g) 0

Cadmium (g) 0


TOTAL (g) 0

No clear recommendation about the necessity of disassembling this component

Pt and Pd will be probably lost during the shredding process if the sensor is not extracted

Precious metals in the sensor (Pt & Pd) implies an economic value for recycling




Name Lambda Sensor





20 31 41 10 15 20 30 46 61




The disassembly cost is 0.51 times the total potential benefit of recycling Pt and Pd


Name Lambda Sensor



Are possible recycling contaminants in the assessed part? Yes


It requires a degree of mech. disassembly before the sensor element can be accessed


Name Lambda Sensor



min avg max


282 428 569






The disassembly cost is 4.76 times higher than the total benefit of recycling Pt and Pd


Name Lambda Sensor



min avg max


313 474 630




The total disassembly cost is 5.27 times higher than the total benefit of recycling Pt & Pd


The motivation of disassembly is only economical (41 mg Pt + 21 mg Pd = 1 € approx.)



In the studied conditions, the disassembly of the lambda sensor is not recommended

5.4 General Comments and Conclusions

Testing and validation of methodologies:

The two methodologies have been successfully tested and validated in 6 case studies.

These methodologies fulfil the requirements and expected goals of SEES Project:

- quantification of need, value, and effort of dismantling EES products

- comparison of design alternatives of EES products

- support in design for dismantling, re-use, recycling and recovery EES products

- prediction of mass & economical consequences of alternative EES end-of-life scenarios

- performance of balances between “disassembly efforts” vs. “end-of-life consequences”

The quality and usefulness of results and conclusions obtained with the application of the methodologies depend on the quality of the input and default data used.



6 ConclusionsIn the next pages are collected the main conclusions obtained in the “EES recycling study”, after studying the recycling possibilities of previously disassembled EES components as well as mixed EES materials from the shredder (mechanical and chemical recycling) and after testing two new methodologies to quantify the recyclability and recoverability potential of EES products and to simulate end-of-life scenarios.

The studied EES components can be grouped in three groups depending on the compos-ition of the EES and depending on the possible recycling routes that can do taking into account the materials and dismantling steps that have been carried out:

Group 1: Cables/Wire harnesses (SEES component group 3) and Electric Motors/Generators (SEES component group 8) can be grouped in this “mechan-ical recycling” because more than the 90% of the material in these products is metal group 8 and more than the 50% of the material is cable in group 3. Because of the high metal content, the mechanical recycling of the components included in these group seems to be the best recycling option.

Group 2: Printed circuit boards containing devices include in this recycling group. Printed circuit board containing devices are the following SEES component groups: Connection/Protection devices (SEES component group 4), Electronic control units (ECU) (SEES component group 5), Integrated mechatronic compon-ents (IMC) (SEES component group 6) and Entertainment (SEES component group 12). Two are the main material fractions, plastic fraction and PCB fraction, in this group.

Presence of PCB s: range from 35-55% weight (*)

(*) This share can be increased since attached components as fuses and re-lays, could be not present.

Material shift in housing from metal (old designs) to plastics (new designs)

Plastics materials for housings not standardised (ABS, PA or PP)

Reversible joints (screws, clips...)

Samples from ELV are dirt and damaged

Plastics predominate, on contrary G8 motors and generators >95% metals or G3 cables >50% metal

Thanks to a first mechanical recycling the PCB fraction and the plastic fraction could be separated in order to treat then the two fractions in different recycling routes. The PCB fraction could continue being treated in a chemical recycling in order to obtain the precious metal of the PCBs and the plastic fraction could con-tinue being in a mechanical recycling in order to obtain recycled plastic fraction with the highest quality. This route combining different recycling routes seems to be the best one.

Group 3. Sensors and actuators, like the lambda sensor, are included in this chemical recycling group. These components usually contain precious metals in



slight quantity that can not be recycled mechanically, because of that the chemical recycling is the best option to recover the precious metals that are presented in these components. Palladium and Platinum are presented in the Lambda sensor for example.

From the technical point of view, mechanical treatment is a good solution for EES com-ponents like the wire harnesses and junction boxes after dismantling these EES compon-ents. It is not only possible to treat it but also to get valuable fractions with a high added value. On one hand it is possible to get concentrated fractions that can be introduced in advanced steps in the metallurgical processes. On the other hand it is recovered the plastic fraction separately. Without metals can be used in cement plants as coque substi-tute, and for energy recovery or can be separated and recycled in order to obtain a high quality recycled plastic fraction.

About motors and alternators there is not a clear solution from the technical point of view in a secondary mechanical treatment plant. The proposal in principle would be to send this fraction to metallurgical process directly. In the end, it would make no sense to dis-mantle these components from the car for recycling purpose because the same copper-iron compound fraction could be easily handpicked after the shredder without prior dis-mantling.

From the technical and economical point of view, the secondary mechanical treatment plants are good solutions for EES mixed fractions from car shredders. On one hand it is possible to give an added value to these fractions that can not be optimized at car shred-ders plants and on the other one, is possible to get more concentrated fractions. These concentrated raw fractions are introduced in advanced stages of metallurgical processes. The added value is enough to pay the mechanical treatment costs, furthermore, it is pos-sible to recover some other fractions like iron and aluminium that otherwise, are lost in copper smelters. The advantage of this process is that is possible to treat a great variety of materials and get valuable fractions with less disassembly effort. The disadvantage is that, in principle, the recovered mixed plastic fraction seems to be more difficult to recycle in new plastic due to the great variety and the previous treatments.

Acidic aqueous chloride solutions containing chlorine have been determined as an appro-priate (regenerable) oxidant for the recovery of metals from electronic scrap, while the work at Imperial College London has firmly established the feasibility of using chlorine in a chlorine leach-electrowin process for the treatment of waste electronic material.

The operating leaching conditions are suggested as at least 5 M chloride ions, a pH of less than zero, and 100molm-3 dissolved chlorine concentration, to drive the dissolution of the metals from the electronic scrap. As discussed above, it is proposed that a packed bed reactor operating in continual mode is likely to yield the best performance for the leaching of metals from EESs. Hence this is the type of reactor which is being designed and on which further experiments are being performed. Given that the dissolution reac-tions are limited by the chlorine gas concentration, it is expected that co-current downflow packed bed (trickle bed) reactor is the best flow arrangement. From considering the ef-fect of mechanical shredding processes on subsequent chemical extraction efficiencies, it is expected that splitting the mechanically treated EESs into two, and leaching the smal-



ler particles in an agitated reactor and the larger ones in a packed column may be the most cost efficient option.

For the recovery of metals from solution, it has been found that semi-selective electrowin-ning at a variety of potentials (e.g. V1 = -0.5 V, V2 = -0.7 V) is the most efficient method of metal recovery. It has also been shown by exhaustive electrolysis that complete re-covery of copper, silver, gold and palladium is possible from the leachate solution in about six hours, at potentials below -0.4 V (SCE), with a high current efficiency. The po-tential can then be stepped down to below -0.6 V (SCE), for essentially complete removal of the tin and lead within a further three hours (also at high current efficiency as both metals are poor catalysts for the evolution of hydrogen). During the electrowinning exper-iments, approximately 20% of the zinc, iron, and nickel deposited as a result of alloy formations, catalysing hydrogen evolution and decreasing current efficiencies. No deple-tion of the aluminium concentration was measured during exhaustive electrolysis, as it is not possible to reduce it from aqueous solutions.

From the value of the recoverable metals present, the value of a typical printed circuit board is around 2931€/tonne. The average current efficiency for the electrowinning ex-periments performed to date has been greater than 90%, giving electrical energy costs of around 147€/tonne of boards processed. Even if, as expected, a compromise in efficiency must be made recovery the lead, zinc, nickel and iron, the costs are still extremely favour-able, at less than 366€/tonne of shredded EESs.

More detailed costs for the process equipment, instruments, and running costs have also been estimated for a plant capable of processing 1 tonne per day of shredded electron-ics. Ten 100 kg/day leach column reactors, 1.6 m in height and 0.3 m in diameter, will be used to dissolve the metals from the WEEE. Fifteen electrochemical reactors, 1 m * 0.3 m * 0.1 m in size and with a circulating particulate bed cathode of area about 5 m2, will be required to recover the metal from solution. Power will be supplied by a 15 V, 3200 A transformer-rectifier. The equipment costs (including reactors, power supply, pumps, fit-tings, valves, instruments, pipe work, sensors, alarms, support frames, buns and reservi-ors) for a 1 tonne per day plant are approximately 161.196€. The assumption that the equipment costs constitute approximately one quarter of the costs for the plant, buildings and services, gives a total capital expenditure to construct and install such a plant of less than 659.437€. Taking into account the expected lifetime for the different items of equip-ment, the total annual capital, operating and refining costs are below 175.850€, com-pared with an annual processed metal value of 732.708€.

In spite of the fact that the conclusions obtained after testing the two methodologies de-veloped in the SEES project in 6 case studies should not be considered as general con-clusions and recommendations applicable to these and other EES products, the most im-portant conclusions about the recyclability of the products can be these ones:

Current disassembly processes (mostly manual) are economically unviable, or in other words, the total disassembly costs are much higher than the total potential benefit of re-cycling EES products. In these conditions, disassembly for material recycling is not re-commended. The alternative end-of-life scenarios studied and tested in the SEES Project (mechanical recycling of boxes and chemical recycling of PCBs) instead of a second manual level disassembly to disassemble the product into its different parts and materi-



als result in more benefits but the total disassembly & recycling strategy is still economic-ally unviable.

In some EES products disassembly would be only justified and recommended in the case that they contain a significant amount of Pb in solder (for example, more than 5 g) and if the overall content of Pb in solder in the total vehicle is above 60 g. In these cases, mechanical recycling of boxes, chemical recycling of PCBs, recycling of plastics, etc. are interesting synergies for compensating disassembly costs. Disassembly for re-using is another interesting strategy, but re-use markets are quite limited for EES products.

Finally, disassembly processes, recycling processes and EES product designs require a very significant optimisation for making the whole strategy economically viable. However, options to improve disassembly by changing EES designs are very limited, as concluded in the disassembly studies performed in the SEES Project (see SEES D3 Report).



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(8) Meccuci A. and Scott K.; J. Chem. Technol. Biotechnol., 2002, 77, 449-457.

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(10) El Gersifi, K., Tersac G., Durand, G.; Recents Progres en Genie des Procedes, 2001, 15 (86, Procedes pour l'Environnement: Eau, Air, Sols), 443-450.

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(17) Martin R., Simon-Hettich B., and Becker J.; Safe Recovery of Liquid Crystal Displays (LCDs) in compliance with WEEE. Proceedings of Electronics Goes Green 2004,



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http://www.sees.eu.com/

http://sees-project.net/





http://www.dti.gov.uk/


8 Appendix

8.1 Appendix 1: Conditioning of PCBs for Chemical Recycling

8.1.1 PCB1. Lead-free samples (Smart & Passive JBs)



8.1.2 PCB2. Electronic Modules (Lead-free)



8.1.3 PCB3. Smart JB passenger



8.1.4 PCB4. Electronic modules (tin-lead)



8.1.5 PCB 5. Passive Junction Boxes



8.2 Appendix 2: Chemical Analysis Data



8.3 Appendix 3: EES components database

8.3.1 Lambda control exhaust gas sensor from EoL vehicle



8.3.2 Wire harness from EoL vehicle



8.3.3 Wire Harness (passenger compartment, OPEL – Vectra)



8.3.4 Passive junction box engine compartment from EoL vehicle



8.3.5 Relay from EoL vehicle



8.3.6 Small fuse from EoL vehicle



8.3.7 Small fuse from EoL vehicle



8.3.8 Passive PCB junction box (passenger compartment)



8.3.9 Smart Junction box (engine compartment, OPEL – Vectra)



8.3.10 Smart junction box (passenger compartment, OPEL – Vectra)



8.3.11 Seat mechatronic (passenger compartment, FIAT)



8.3.12 Electronic Control Unit (passenger compartment, MATRA)



8.3.13 Alternator from EoL vehicle



8.3.14 Starter motor from EoL vehicle



8.3.15 Cassette player / radio from EoL vehicle


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