database reactive materials

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5th Framework ProgrammeResearch and Technological Development Project

Long-term Performance of Permeable ReactiveBarriers used for the Remediationof Contaminated Groundwater

PEREBAR

Database:

Properties of Reactive Materials suitable for usein Permeable Reactive Barriers

by

National Technical University of AthensDepartment of Mining And Metallurgical EngineeringLaboratory of MetallurgyGR-157 80 Zografos, Athens, Greece

April 2002

Project Contract Number: EVK1-CT-1999-00035Project Web Site: http://www.perebar.bam.de/


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PPEERREEBBAARR EVK1-CT-1999-00035 Reactive Materials / April 2002

TABLE OF CONTENT

1. INTRODUCTION..................................................................................................................2

2. CHARACTERIZATION OF REACTIVE MATERIALS ...................................................................3

2.1 Zero-valent Iron .......................................................................................................3

2.1.1 Chemical Analysis........................................................................................3

2.1.2 Mineralogical Analysis..................................................................................3

2.1.2.1 X-ray Diffraction (XRD).................................................................... 3

2.1.2.2 Thermogravimetric Analysis............................................................4

2.1.3 Physical Characteristics............................................................................... 4

2.2 Activated Carbon.....................................................................................................5

2.2.1 Elemental Analysis.......................................................................................5




2.3 Natural Zeolitic Tuff ................................................................................................. 6






2.4 Hydroxyapatite ........................................................................................................7






2.5 Lime.........................................................................................................................8

2.5.1 Chemical Analysis........................................................................................82.5.2 Mineralogical Analysis..................................................................................8


2.5.2.2 Thermogravimetric analysis ............................................................9


3. REFERENCES .................................................................................................................10

APPENDICES ..................................................................................................................11

Appendix A: Chemical AnalysisAppendix B: Technical Data Sheets

Appendix C: Cost of Materials

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1. INTRODUCTION

One of the most promising treatment technologies for groundwater remediation by means ofreactive materials, which combines the effective removal of various contaminants with a lowconstructional and operational cost, is the so called Permeable Reactive Barriers (PRB)

technology. The reactive materials are placed in underground trenches downstream of thecontamination plume forcing it to flow through them, and by doing so the contaminants areimmobilized or decomposed without soil or water excavation (Smyth et al. 1997). Thearrangement of a Permeable Reactive Barrier is illustrated in Figure 1.

Figure 1: Schematic view of a permeable reactive barrier installation

The selection of the reactive materials is based on the type of contaminants that the plum

consists of. However, there are some properties that characterize a medium suitable for theconstruction of a permeable reactive barrier (Gavaskar et al. 1997):

Reactivity: The reactivity of the material is quantitatively evaluated by the requiredresidence time or the reaction rate constant. It is desirable to have low residence timesand high reaction rates in order to keep the thickness of the barrier within acceptablelimits.

Stability: The material is expected to remain active for long periods of time because itsreplacement is not easily achieved. Stability in changes of pH, temperature, pressure andantagonistic factors is also required.

Availability and cost: The amount of the reactive material required for the construction ofa reactive barrier is large enough and therefore it is essential to have considerablequantities in low prices.

Hydraulic performance: The hydraulic conductivity of the material depends on its particlesize distribution and its value must be greater or equal to the value of the surroundingsoil. However, an optimum particle size that would provide appropriate permeability andsufficient contact time must be determined.

Environmental compatibility: It is important that the reactive media do not form anybyproducts when reacting with the contaminants and that it is not a source of

contamination itself by solubilization or other mobilization mechanisms.

Safety: Handling of the material should not generate any risks for the health of workers.

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In general, the types of reactive materials used for the construction of permeable reactivebarriers, area) those changing pH or redox potential,b) those causing precipitation,c) materials with high sorption capacity, andd) those releasing nutrients/oxygen to enhance biological degradation.

Some common reactive media along with their properties are presented in the followingparagraphs. These materials were used for laboratory and field case studies within thePEREBAR project (Long-term performance of Permeable Reactive Barriers used for theremediation of contaminated groundwater).

2. CHARACTERIZATION OF REACTIVE MATERIALS

2.1 Zero-valent Iron

Zero-valent iron (Fe0) is the most common reactive material in current field applications

(OHannesin and Gillham 1992). Metallic iron has been evaluated by a number oflaboratories for its potential use as a reactive material to minimize the subsurface migrationof certain reducible metal ions (Cantrell 1995). In situ treatment technologies are developedtaking advantage of chemical reactions at the surface of zero-valent Fe which are capable oftransforming or degrading contaminants into non-toxic or immobilized chemical forms(Gillham and OHannesin 1994, Argawal and Tratnyek 1996, Blowes et al. 1997). Theextensive use of iron is attributed to its ability to degrade several organic substances andsome inorganic compounds such as chromium, nickel, lead, uranium, arsenic, among others.The degradation rate depend primary on the specific surface area of iron. In addition,granular iron is the cheapest metallic media available, and one of the cheapest reactivematerials in general.

The zero-valent iron sample studied by NTUA for the PEREBAR project was supplied byGotthart Maier, German and is characterized as cast iron grit.

2.1.1 Chemical Analysis

Chemical analysis showed that the zero-valent iron consists mainly by Fe (92.03% w/w), C(3.31% w/w), Si (2.04% w/w) and other elements such as Mn, Al, S, Ni, Cr and P in lowerconcentrations. These results together with the chemical analysis of the other investigatedreactive materials are summarised in Table 1 in Appendix A.

2.1.2 Mineralogical Analysis

2.1.2.1 X-ray Diffraction (XRD)

Mineralogical investigation carried out by X-ray diffraction and Scanning electron microscopy(accelerated voltage: 25KV) revealed the existence of metallic iron, graphite and iron oxide(about 10%). Figures 2 and 3 present the XRD diagram and scaning electron microscopyimages, respectively.

2.1.2.2 Thermogravimetric Analysis

Thermogravimetric analysis confirmed the absence of any degradable mineral phases.Figure 4 presents the TG diagram of the zero-valent iron sample, obtained at a temperaturerange between 110.00 and 980.00C and a rate of 20.00 deg/min.

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Figure 2: XRD diagram for the zero-valent iron sample.

(a) (b)

Figure 3: SEM images of ZVI; (a) at low (x 12) and (b) high (x 45) resolution.

2.1.3 Physical Characteristics

The paste pH of zero-valent iron was equal to 5.1-5.3. A BET analysis was applied using aNOVA-1200 Ver.5.01 instrument. Nitrogen with a Po equal to 757.36 mmHg was used asadsorbate and the specific surface area of the material was measured equal to 0.0482 m2/g.As stated in the technical data sheet (Appendix B) provided by Gotthart Maier, Germany, thegrain size of the delivered material was equal to 0.20-1.00 and 0.35-1.20 mm. The apparentdensity of the sample was 2.7-2.9 g/cm3. These results as well as the physical properties ofthe other studied materials are summarised in Table 1 in Appendix A.

Figure 4: TG diagram of the zero-valent iron.

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2.2 Activated Carbon

Activated carbons are chemically stable materials and are widely considered as suitableadsorbents for on-site or off-site treatment of polluted groundwater (Roehl et al. 2001). Thismaterial presents a high adsorption capacity for many organic and inorganic contaminantsmostly owning to its large specific surface area (around 1000 m2/g by N2-BET) and the

presence of different types of surface functional groups. In granular form, activated carbonappears to be highly suitable for use in permeable barriers (Han et al. 2000).

The activated carbon sample studied by NTUA was provided by Donau Chemie, Austria bythe trade name DonauCarbon CC15 in the form of cylindrical pellets.

2.2.1 Elemental Analysis

Elemental analysis was performed using a LECO CS-200 microanalysis apparatus. Activatedcarbon was found to consist of carbon at a percentage of about 83% w/w. This result is alsopresented in Table 1 in Appendix A.



As shown in Figure 5, thermogravimetric analysis (rate: 20 deg/min) of the sample showedonly the loss of pore water. The analysis was carried out at a temperature range between40.00 and 980.00C.


Donau Chemie, Austria, provided a technical data sheet (Appendix B) with the physicalproperties of the delivered product. The specific surface area of the material is 1000 m2/gminimum measured in accordance with the method suggested by the DIN 66131, while theparticle size is 1.5-4 mm. Other physical characteristics of the sample are the apparentdensity which is 0.45 g/cm3 ( 10%), ash less than 12% and iodine number (ASTM D4607-

94) greater than 950 mg/g. These properties along with the physical characteristics of theother materials are summarized in Table 1 in Appendix A.

Figure 5: Thermogravimetric analysis of the activated carbon sample.

2.3. Natural zeolitic tuff

Natural zeolites are crystalline aluminosilicates, the structure of which is based on tetrahedralSiO4 and AlO4 units that are connected by shared oxygen atoms. Exchangeable cations and

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water molecules are located in the channels of the framework. The general composition ofthe zeolites can be represented by My/z [(SiO2)x(AlO2)y] nH2O where M is the exchangeablewith a valence z. At least 70 different zeolite structures are known. In natural zeolites theSi/Al ratio varies in the range of 1-6, and for most of the naturally occurring types, syntheticanalogues have been prepared (Akyil et al. 1998).

The sample of natural zeolitic tuff originated from the exploitations of Silver & Baryte MiningCo. in Pentalofos, Greece and it was crushed and milled upon delivery. The material can beprovided in bags of 25 Kgs or 1 MT each, while the prise of zeolite is 145 Euros/MT. The costof the zeolite together with the cost of the other materials is presented in Appendix C.


Chemical analysis of natural zeolite was performed using HF, HNO3, HClO4 and HCl. Thesample was found to contain 68.98% SiO, 14.17% Al2O3, 3.85% K2O, 3.71% CaO, 2.40%MgO, 2.37% Fe2O3, 2.31% Na2O, 0.39 % TiO2, 0.06% MnO as well as 7.9% H2O.



The mineralogical composition of natural zeolite is comprised primary of clinoptilolite-heulandite (85%) and additionally of mica, plagioclase, montmorillonite and quartz. The XRDimage of zeolite is shown in Figure 6a.


Figure 6b illustrates the TG-DTG diagrams obtained for the natural zeolitic tuff. Themeasurements were carried out at a temperature range of 40.00-940.00 C and with a rate of20.00 deg/min.

(a) (b)

Figure 6: XRD-diagram (a) and TG-DTG (b) diagram of the natural zeolite sample.


The zeolite cages have dimensions of about 5 , while other physical properties of thematerial include a pore volume equal to 0.34 cm3/cm3, an apparent density equal to 0.85-1.1 g/cm3 and an alkaline stability and acidic stability equal to 7-11 pH and 2-7 pH,respectively. The cation exchange capacity (CEC) of the material is 150 meq/100g minimum.The granules of the sample are equal to 0-1.2 and 0-0.15 mm. These properties aresummarised in Table 1 in Appendix A, while the corresponding technical data sheet is

presented in Appendix B.

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2.4. Hydroxyapatite

The hydroxyapatite sample was provided by BAM (Berlin) in two different grain sizes.


Chemical analysis of hydroxyapatite was performed using HNO3 and HCl. The sample was

found to contain 61.81% CaO, 41% P2O5, 0.43% MgO, and lower quantities of K2O, Fe2O3and MnO. The results of the chemical analysis of hydroxyapatite are presented in Table 1 inAppendix A.



The mineralogical investigation by XRD revealed the existence of three types ofhydroxylapatite which are primarily Ca5(PO4)3(OH), Ca5(PO4)3(OH,Cl,F) andCa10(OH)2(PO4)610CaO3P2O3H2O) and no other accessory mineral. Figure 7b illustrates theXRD diagram.

2.4.2.2 Thermogravimetric AnalysisThermal loss as indicated by DTA-TG analyses accounted for 4% approximately,representing mainly crystal water. The corresponding DTA-DTG diagram is shown in Figure7a.

(a) (b)

Figure 7: DTA-DTG (a) and XRD (b) diagram for the hydroxylapatite sample.


The paste pH of the hydroxyapatite sample is equal to 6.5, while the granule size varies from0-1.25 and 0-2.00mm. The specific surface area of the delivered sample is equal to 65m2/g.These characteristics are summarised in Table 1 in Appendix A.

2.5 Ca(OH)2 (Lime)

The hydrated lime sample was obtained by Mosholios S.A, which is a Greek tradingcompany in industrial grade. The cost of the material is 0.132 /Kg (Appendix C).


Chemical analysis of the lime sample was performed using HF, HNO3, HClO4 and HCl. Limewas found to consist primary of CaO at a percentage of 83.96% and of other substances

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such as MgO, MnO, Fe2O3, K2O and Na2O at lower concentrations. The results obtainedfrom the chemical analysis of lime are presented in Table 1 in Appendix A. The informationprovided by the company stated that the sample contains 85-91% Ca(OH)2, 1% phosphates,1.5% max Mg, 5% grit, while the total solids are 5%.



According to the mineralogical analyses the sample consists of portlandite Ca(OH)2 andcalcite (CaCO3). The XRD diagram is presented in Figure 8.


The thermogravimetric analysis diagram of the lime sample is shown in Figure 9.

Figure 8: XRD diagram of the Ca(OH)2.

Figure 9: TG diagram of the lime sample.


The paste pH of the material is equal to 12.4. The company provided the NTUA withinformation regarding the characteristics of lime concerning the granulometry of the sample(99.5% of the granules have a diameter less than 0.59 mm, the diameter of the 94.4% is lessthan 0.09 mm, while for the rest 5.55% of the sample the diameter is between 0.09 and0.59 mm).

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3. REFERENCES

Akyil, S., Aslani, M.A.A. and Ayta. . (1998): Distribution of uranium on zeolite Xinvestigation of thermodynamic parameters for this system. Journal of Alloys andCompounds, 271/273, 769-773.

Argawal, A. and Tratnyek, P.G. (1996): Reduction of nitro aromatic compounds by zero-valent iron metal. Environ. Sci. Technol., 30, 153-160.

Blowes, D.W., Ptacek, C.J. and Jambor, J. L. (1997): In-situ remediation of chromatecontaminated groundwater using permeable reactive walls. Environ. Sci. Technol., 31, 153-160.

Cantrell, K.J., Kaplan, D.I. and Wietsma, W. (1995): Zero-valent iron for the in-situremediation of selected metals in groundwater. Journal of Hazardous Materials, 42, 201-212.

Gavaskar, A.R., Gupta, N., Sass, B., Fox, T., Janosy, R., Cantrell, K. and Olfenbuttel, R.

(1997): Design guidance for application of permeable barriers to remediate dissolvedchlorinated solvents. AL/EQ-TR-1997-0014, United Stated Air Force, Armostrong Laboratory,Battelle, p.104.

Gillham, R.W. and OHannesin, S.F. (1994): Enhanced degradation of halogenated aliphaticsby zero-valent iron. Ground Water, 32, 958-967.

Han, I., Schlautman, M.A. and Batchelor, B. (2000): Removal of hexavelent chromium fromgroundwater by granular activated carbon. Wat. Env. Res., 72, 29-39.

Matheson, L.J. and Tratnyek, P.G. (1994): Reductive dehalogenation of chlorinatedmethanes by iron metal. Environ. Sci. Technol., 28, 2045-2053.

Roehl, K.E., Huttenloch, P. and Czurda, K. (2001): Permeable sorption barriers for in-situremediation of polluted groundwater - reactive materials and reaction mechanisms. In:Sarsby, R.W. & Meggyes, T. (eds.), GREEN 3, 3rd International Symposium on GeotechnicsRelated to the European Environment, June 21-23, 2000, Berlin, Germany. Thomas Telford,London, 466-473.

Smyth, D.A., Shikaze, S.G. and Cherry, J.A. (1997): Hydraulic performance of permeablebarriers for the in situ treatment of contaminated groundwater. Land Contamination &Reclamation, 5(3), 131-137.

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APPENDIX A

Chemical Analysis

Table 1: Chemical analysis and physical properties of the investigated reactivematerials.

(% w/w)Zero-

valent ironActivated

carbon(% w/w)

Naturalzeolite

Hydroxyapatite Ca(OH)2

Fe 92.03 Fe2O3 2.37 0.04 0.04

C 3.31 83 Na2O 2.31 0.09 0.01

Si 2.04 SiO2 68.98

Mn 0.63 MnO 0.06 0.01 0.22

Al 0.16 Al2O3 14.17

S 0.09 0.36 CaO 3.71 61.81 83.96Ni 0.06 MgO 2.40 0.43 0.28

Cr 0.05 TiO2 0.39

P 0.04 K2O 3.85 0.03 0.03

P2O5 41.00

Mg1.5%max

SO42- 1%

H2O 0.4 5.45 H2O 7.90

Paste pH 5.1-5.3 10.23 pH 7.87 6.5 12.38

CEC (meq/g) 1.50Specificsurface area(m2/g)

0.0482 1000 15.58 60

Granulometry(mm)

0.2-1.00.35-1.2

1.5-4.00-1.200-0.15

0-1.250-2.00

0-0.090-0.59

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APPENDIX B

Technical Data Sheets

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APPENDIX C

Cost of Materials

Material Cost

Zeolite 145 /Metric ton

Activated carbon 613 /ton

Lime Ca(OH)2 0.132 /Kg

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