university grants commission research project: by dr. b. n. kokare, raje ramrao mahavidyalaya, jath,...

Minor Research Project: By Dr. B. N. Kokare, Raje Ramrao Mahavidyalaya, Jath, Sangli (M.S.)

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Liquid anion-exchange extraction and separation of

precious metals by using High Molecular Weight

Amine (HMWA) as a metallurgical extractant.

MINOR RESEARCH PROJECT

FINIAL WORK DONE REPORT

(07-06-2014 to 06-06-2016)

Submitted to

UNIVERSITY GRANTS COMMISSION

WESTERN REGIONAL OFFICE, PUNE

By

Dr. Shrikant R. Kokare Dr. Balasaheb N. Kokare M. Sc., Ph. D. M. Sc., Ph. D.

Co- Investigator and Head Principal Investigator and Head,

Post Graduate Department of Physics, Post Graduate Department of Chemistry,

Raje Ramrao Mahavidyalaya, Jath

2017


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INDEX

Sr.

No.

Details Page

No.

1 Audited Consolidated Statement of Expenditure with item wise

details under ‘non-recurring & ‘recurring’ heads for the amount

actually incurred duly signed by the Principal & C. A. with stamp &

Registration No. Annexure III (Annual)

2 Statement of Expenditure on Field Work in the prescribed

formats as per UGC guidelines. Annexure IV (Annual)

3 Audited Consolidated Utilization Certificate for the amount

actually incurred, duly signed by the Principal & C. A. with

stamp. Annexure V (Annual)

4 Annual Report of the work done of the Minor Research

Project. Annexure VI (Annual) and Appendix-I

5 Audited Consolidated Statement of Expenditure with item wise

details under ‘non-recurring & ‘recurring’ heads for the amount

actually incurred duly signed by the Principal & C. A. with stamp &

Registration No. Annexure III (Final)

6 Statement of Expenditure on Field Work in the prescribed

formats as per UGC guidelines. Annexure IV (Final)

7 Audited Consolidated Utilization Certificate for the amount

actually incurred, duly signed by the Principal & C. A. with

stamp. Annexure V (Final)

8 Certificate (Utilization of grant within tenure)

9 Accession Certificate (Books and Journal)

10 Assets Certificate (Equipments)

11 A copy of the proof about uploading of Executive summary of

the report, Research documents, monograph, papers published

under Minor Research Project on the website of the College

12 Final Report of the work done of the Minor Research Project.

Annexure VI (Final) and Appendix-II

13 Proforma for submission of information at the time of sending the

final report of the work done on the project Annexure VII (Final)

14 Work Done in the prescribed format Chapters I, II, III & IV

15 Publications

16 Acknowledgements


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Appendix – I (Annual)

Report of the work done in First Year

Project Title : “Liquid anion-exchange extraction and separation of

precious metals by using High Molecular Weight Amine (HMWA)

as a metallurgical extractant”

1) In the first phase, reference work and literature survey on high molecular weight amine

and their synthesis is done. Chemicals, glass wares and equipments for project work are

purchased.

2) Synthesis of 4-Heptylaminopyridine (High Molecular Weight Amine)

To a stirred solution of 4-aminopyridine (0.05 mol) in dry THF (40 mL), sodium

amide was added at 0oC and continued stirring for 30 min. The temperature of the reaction

mixture increased to room temperature and 1-bromoheptane was added slowly. The reaction

mixture was stirred at the ambient temperature for 1 h. The reaction mixture was poured into

water containing NH4Cl and extracted with chloroform (150 mL). The chloroform extract

was dried (Na2SO4) and evaporated on a rotary evaporator to yield a residue which was

crystallized to afford the corresponding 4-heptylaminopyridine.

N

NH2

+ NaNH2

N

NH

+ NH3

Na

THF/ Stirr

0 oC

+

N

NH Na

StirrBr-CH2-(CH2)5-CH3

1 hr.

N

NH-CH2-(CH2)5-CH3

+ NaBr

3) 4-Heptylaminopyridine is white solid, which is readily soluble in xylene, toluene, benzene,

carbon tetrachloride, chloroform and acetone. Recrystallisation involves huge losses. We


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recrystallised 4-heptylaminopyridine from acetone and obtained a product containing 99.9%


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Annexure – III (Final)


BAHADUR SHAH ZAFAR MARG

NEW DELHI – 110 002

STATEMENT OF EXPENDITURE IN RESPECT OF MINOR RESEARCH

PROJECT

1. Name of Principal Investigator : Dr. B. N. Kokare

2. Department of PI : Chemistry

Name of College : Raje Ramrao Mahavidyalaya, Jath Dist-Sangli

3. UGC approval letter No. & date : No 47-601/13(WRO), date: 26 March 2014

4. Title of the Research Project : Liquid anion-exchange extraction and

separation of precious metals by using High

Molecular Weight Amine (HMWA) as a

metallurgical extractant

5. Effective date of starting the Project: 07-06-2014

6. a. Period of Expenditure : From 07-06-2014 to 06-06-2016

b. Details of Expenditure

Sr.

No.

Item Amount

Approved in Rs.

Expenditure

Incurred in Rs.

i Books and Journals 20000 20000

ii Equipment 250000 250000

iii Contingency 20000 20126

iv Field Work / Travel 25000 25358

v Special Need (Hiring Services,

Spectra analysis)

40000 40070

vi Chemicals and Glassware 80000 80100

Total 435000 435654

7. If as a result of check or audit objection some irregularly is noticed at later date,

action will be taken to refund, adjust or regularize the objected amounts.


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Annexure –VI Final



NEW DELHI – 110 002.

Final Report of the work done on the Minor Research Project

(Report to be submitted within 6 weeks after completion of each year)

1. Project Report No. 1st / Final : Final

2. UGC Reference No. F. : 47-601 / 13 (WRO), dated 26 March 2014

3. Period of report : from 07-06-2014 to 06-06-2016

4. Title of research project : Liquid anion-exchange extraction and

separation of precious metals by using High

Molecular Weight Amine (HMWA) as a


5. (a) Name of the Principal Investigator : Dr. B. N. Kokare

(b) Department : Chemistry

(c) College where work has progressed: Raje Ramrao Mahavidyalaya, Jath

6. Effective date of starting of the project : 07-06-2014

7. Grant approved and expenditure incurred during the period of the report:

(a) Total amount approved Rs. : 4,35,000/-

(b) Total expenditure Rs. : 4,35,654/-

(c) Report of the work done : Separate sheet is attached (Appendix–I)

i. Brief objective of the project :

1) To synthesize 4-heptylaminopyridine (High Molecular Weight Amine). The main

objective is to determine optimum conditions for extraction of precious metals.

2) To analyze synthesized 4-heptylaminopyridine (High Molecular Weight Amine) by

spectral analysis like 1H NMR and IR.


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Appendix – II Final

Final Report of the Work Done

(First & Second Years)

Project Title: Liquid anion-exchange extraction and separation of precious

metals by using High Molecular Weight Amine (HMWA) as a


First Year:

1) In the first phase, reference work and literature survey on high molecular weight

amine and their synthesis is done. Chemicals, glass wares and equipments for project

work are purchased.

2) Synthesis of 4-Heptylaminopyridine (High Molecular Weight Amine)

To a stirred solution of 4-aminopyridine (0.05 mol) in dry THF (40 mL),

sodium amide was added at 0oC and continued stirring for 30 min. The temperature of

the reaction mixture increased to room temperature and 1-bromoheptane was added

slowly. The reaction mixture was stirred at the ambient temperature for 1 h. The

reaction mixture was poured into water containing NH4Cl and extracted with

chloroform (150 mL). The chloroform extract was dried (Na2SO4) and evaporated on a

rotary evaporator to yield a residue which was crystallized to afford the corresponding

4-heptylaminopyridine.

N

NH2

+ NaNH2

N

NH

+ NH3

Na

THF/ Stirr

0 oC


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Annexure – VII Final



NEW DELHI – 110 002

PROFORMA FOR SUBMISSION OF INFORMATION AT THE TIME OF SENDING

THE FINAL REPORT OF THE WORK DONE ON THE PROJECT

1. Title of the Project: “Liquid anion-exchange extraction and separation of

precious metals by using High Molecular Weight Amine (HMWA) as a

metallurgical extractant”.

2. NAME AND ADDRESS OF THE PRINCIPAL INVESTIGATOR: Dr. B. N. Kokare,

Department of Chemistry, Raje Ramrao Mahavidyalaya, Jath Dist- Sangli.

3. NAME AND ADDRESS OF THE INSTITUTION: Raje Ramrao Mahavidyalaya, Jath

Dist- Sangli 416 404.

4. UGC APPROVAL LETTER NO. & DATE: 47-601/13(WRO), dated: 26 March 2014

5. DATE OF IMPLEMENTATION: 07/06/2014

6. TENURE OF THE PROJECT: Two years (07/06/2014 to 06/06/2016)

7. TOTAL GRANT ALLOCATED : 4,35,000/-

8. TOTAL GRANT RECEIVED: 3,52,500/-

9. FINAL EXPENDITURE : 4,35,654/-

10. TITLE OF THE PROJECT: “Liquid anion-exchange extraction and separation

of precious metals by using High Molecular Weight Amine (HMWA) as a

metallurgical extractant”.


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11. OBJECTIVES OF THE PROJECT :

a) To synthesize high molecular weight amine (4-heptylaminopyridine).

b) Characterization of synthesized high molecular weight amine (4-

heptylaminopyridine).

c) The main objective is to develop solvent extraction method by using 4-

heptylaminopyridine for the extraction of palladium(II) and platinum(IV).

12. WHETHER OBJECTIVES WERE ACHIEVED (GIVE DETAILS):

a) High molecular weight amine (4-heptylaminopyridine) was easily synthesized.

b) The structure of synthesized high molecular weight amine (4-

heptylaminopyridine) is characterized by spectral analysis like 1H NMR and

FT-IR.

c) The synthesized high molecular weight amine (4-heptylaminopyridine) was

used to extract palladium(II) and platinum(IV).

13. ACHIEVEMENTS FROM THE PROJECT

a) Synthesis of new high molecular weight amine (4-heptylaminopyridine).

b) Characterization of these high molecular weight amine by spectral analysis.

d) Development of solvent extraction method for the extraction of palladium(II)

and platinum(IV).

14. SUMMARY OF THE FINDINGS ( IN 500 WORDS ):

High molecular weight amine (4-heptylaminopyridine) was easily synthesized

and characterization was done by using NMR and IR.


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a) IR spectrum

The IR spectrum of 4-heptylaminopyridine (Fig. 1) showed absorption band at 3427

cm-1 due to presence of –NH while at 1646 and 1545 cm-1 indicated presence of

carbon-nitrogen and carbon-carbon double bond respectively.

IR: 3427 (-NH (S)), 3052 (-CH, Ar.), 2957-2855 (-CH (S) (aliph.)), 1646 (-C=N (S)),

1545 (C=C) cm-1.

b) NMR Spectrum

Proton resonance assignments for the pure product were made using TMS as an

internal standard and chemical shift expressed in values, PMR (CDCl3, 300 MHZ,

Fig. 2).

NMR: CDCl3 (300 MHZ): , 0.851 (3H, t, -CH3); 1.61-1.81 (2H, m, -CH2); 2.4 (2H,

qn, -CH2); 3.23 (2H, qn, -CH2); 3.42 (2H, qn, -CH2); 4.35 (2H, qn, -CH2); 4.81 (2H, q,

-CH2); 6.5 (1H, S, -NH); 6.8-8.4 (4H, m, Ar-H) ppm.

The main objective of the project is to develop solvent extraction method for

the extraction of palladium(II) and platinum(IV).

1) Solvent extraction procedure for palladium(II)

In all the extraction studies, aqueous (Pd(II) ion in appropriate concentration

and 0.04 M sodium salicylate, pH was adjusted to 0.5) and organic (0.05 M 4-HAP in

xylene) phases in a ratio of 2.5:1 were shaken at room temperature in glass stoppered

separating funnel for 5 min. After phase disengagement, the aqueous phase was

separated, and loaded organic phase was stripped with 6.0 M ammonia (2 × 10 mL).

The concentration of palladium(II) from stripped solution was determined

spectrophotometrically using dithizone method [76].

2) Solvent extraction procedure for platinum(IV)

An aliquot of 200 µg of platinum(IV) solution was mixed with 0.0308 g of

ascorbic acid to make a concentration of 0.007 M in a total volume of 25 mL of the

solution. The pH of the aqueous solution was adjusted to 1.5 using dil. sodium


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hydroxide and hydrochloric acid solution. The solution was then transferred into a 125

mL separating funnel and shaken with 10 mL of 0.06 M 4-heptylaminopyridine in

xylene for 2 min. After separating the two phases, the aqueous phase was discarded

and the organic phase was stripped with two 10 mL portions of water solution. After

being stripped with water, platinum(IV) was put into the aqueous phase quantitatively.

The stripped aqueous phase was evaporated to moist dryness and extracted into dil.

hydrochloric acid.

15. CONTRIBUTION TO THE SOCIETY (GIVE DETAILS)

The noble metals are resistant to corrosion and oxidation in moist air, unlike most

base metals. They tend to be precious, often due to their rarity in the earth’s crust.

Noble metals are rare, naturally occurring metallic chemical element of high economic

value. Historically, precious metals were important as currency but are now regarded

mainly as investment and industrial commodities. The determinations of these metals

in various samples have become increasingly important.

Solvent extraction procedure for palladium(II)









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Solvent extraction procedure for platinum(IV)










hydrochloric acid.

Advantages: (i) A low concentration of extractant is required for the quantitative extraction of

palladium(II) and platinum(IV).

(ii) 4-Heptylaminopyridine forms an ion–pair complex with palladium(II) and

platinum(IV) in weak acid medium.

(iii) Extraction of palladium(II) and platinum(IV) has been carried out without the

addition of any synergent or modifier at room temperature.

(iv) Ecofriendly strippant (water) is used for the stripping of platinum(IV); its use in

this method follows one of the principles of green chemistry.

v) The developed method is free from interference from a large number of diverse

ions which are commonly associated with palladium(II) and platinum(IV). The

selectivity was also enhanced using suitable masking agents.


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Chapter I

General Introduction


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Solvent Extraction

In recent years, liquid-liquid extraction has come to the front in analytical

chemistry as a popular separation art because of its quickness, absence of

complication and relevance to both macro and tracer amounts of metal ions. The

conditions of liquid-liquid extraction with its relevance are very well explained [1, 2].

Solvent extraction is based on the principle that the partition of solute in a

certain ratio between two immiscible liquid, one of which is usually organic solvent

and the other is water. In certain cases the solute can be transferred into the organic

phase more or less completely. The technique can be used for purposes of purification,

preparation, separation, enrichment and analysis, on all scales of working, from

microanalysis to production processes.

Solvent extraction may be an important step in the sequence that leads a pure

product in the organic, inorganic, or biochemical laboratory. Although complicated

apparatus is sometime employed, frequently only a separatory funnel is required.

Often a solvent extraction separation can be accomplished in a few minutes. The

technique is applicable over a wide concentration range and has been used extensively

for the isolation of extremely minute quantities of carrier-free isotopes obtained by

nuclear transmutation as well as industrial materials produced by the ton. Solvent

extraction separations are usually “clean” in the sense that there is no analog of co

precipitation with such system [3].

Solvent extraction process consists of following steps:

1. Consistent contacting of organic solvent with the aqueous phase containing

solute.

2. The solute is transferred from aqueous phase to the organic phase.

3. Equilibration of two liquid phases.

4. Separation of two immiscible liquid phases.

5. Stripping of solute from the organic phase to aqueous phase by the use of

suitable strippants.

Proceedings of International Conference on Solvent Extraction [ISEC] [4-21] is a

good sources of information on the solvent extraction and provide important records

of the latest developments and trends in solvent extraction. Information about solvent


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extraction are very well explained in several monographs by Morrison and Freiser

[22], De, Khopkar and Chalmers [2], Sekine and Hasegawa [23], Alders [24], Starry

[25], Hanson [26], Marcus and Kertes [27].

Principles of solvent extraction

1) The distribution coefficient:

The distribution equilibrium between two liquid phases is governed by the

Gibbs phase rule, which stated mathematically as,

P + V = C + 2

Where, P = number of phases, V = degree of freedom and C = number of component.

In case of solvent extraction there are two phases namely aqueous and organic, while

solute is only the component in solvent and water phases and at constant temperature

and pressure.

i.e. P = 2, C = 1 and V = 1

At constant pressure and temperature, the rule predicts a variance of unity. This

means if we chose the solute concentration in one phase, the concentration of solute in

other phase is fixed. Hence there will be definite relation between the concentrations

of solute in each of the solvent. Phase rule predicts that a system consisting of two

immiscible solvents and one distributing solute has one degree of freedom. The ratio

of solute concentration is shown to be invariant i.e. independent of total concentration.

The relation between solute concentrations in both the phases is described by

distribution law.

2) The distribution law:

The distribution law is derived in 1898 by W. Nernst and it is related to the

distribution of a solute in the two immiscible liquids. For the equilibrium reaction

A (aq) A (org)(1)

The Nernst distribution law is written

KD =Concentration of Species A in organic phase

Concentration of Species A in aqueous phase=

[A]org

[A]aq

Where, KD = Distribution constant of the solute A


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Strictly, this equation is valid only with pure solvents. In practice, the solvents are

always saturated with molecules of the other phase; e.g., water in the organic phase.

3) The distribution ratio (D):

The IUPAC definition of the distribution ratio (D), for a metal species M can

be written as

𝐷𝑀 =𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑎𝑙𝑙 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑖𝑛𝑔 𝑀 𝑖𝑛 𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑝ℎ𝑎𝑠𝑒

𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑎𝑙𝑙 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑖𝑛𝑔 𝑀 𝑖𝑛 𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑝ℎ𝑎𝑠𝑒

=[𝑀𝑡]𝑜𝑟𝑔

[𝑀𝑡]𝑎𝑞

(2)

When M is present in various differently complexed forms in the aqueous phase and

in the organic phase, [M t] refers to the sum of the concentrations of all M species in a

given phase (the subscript t indicates total M). It is important to distinguish between

the distribution constant (KD), which is valid only for a single specified species (e.g.,

MA2), and the distribution ratio (D), which may involve sums of species of the kind

indicated by the index, and thus is not constant.

4) Relation between distribution ratio and percentage extraction:

𝐷 =[𝑉𝑊

𝑉𝑂] 𝐸

(100 − 𝐸) (3)

Where, Vw is volume of aqueous phase

Vo is volume of organic phase

When volume of organic and aqueous phase are equal i.e. VO = VW, D reduces to

𝐷 =𝐸

100 − 𝐸 (4)

Further the extraction is considered to be quantitative when E = 100, under these

circumstances.

0

100

100100

100D (5)

5) Separation factor (α):

The separation factor (SF) is given by the ratio of distribution ratios of two

different metals. It is a measure of the ability to separate two metals from each other.


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According to IUPAC nomenclature the separation factor is denoted by ‘α’. The

separation factor ‘α’ is related to the individual distribution ratios as follows:

α =𝐷𝐴

𝐷𝐵 (6)

Where DA and DB is the distribution ratio of metal A and B respectively.

Classification of solvent extraction system

Nowadays, large numbers of commercial extractant are available for solvent

extraction and related technologies. Also so many researchers are taking efforts to

produce new reagents. The role of extractant in metal extraction is to form metallic

lipophile complexes which can be transferred from the aqueous phase to the organic

phase through a chemical interaction.

Several extraction mechanisms can be enumerated

1. Extraction by ion-pair formation

I) Anion exchange

Basic extractants (B) are organic reagents which can easily form a salt in the

organic phase while in contact with an aqueous acid solution (HX)

Borg + HXaq →BH+X-org (I)

Where the subindexes org and aq denote the organic phase and aqueous phase

respectively. Then, contacting the organic phase with an aqueous solution containing

anionic metal species MXn-(n-m) (n>m), anoin exchange occurs as follows:

(n-m) BH+X-org + MXn

-(n-m)aq → (BH+

(n-m)MX n-(n-m))org + (n-m)X-

aq (II)

Thus, the amine salt should be considered as being the extracting reagent and

not the free amine.

High-molecular weight amine and quaternary ammonium halide are basic

extractants currently used in solvent extraction process.

e.g. Extraction of Re(VII) from nitrate media with secondary amine.

RR'NH(org)

+ HNO3

(aq)

+ RR'NH2 NO3

-

RR'NH2 NO3

+ -

(org)

(org)

+ ReO4

-

(aq)[RR'NH2

+ReO4

-

(org)NO3

-

(aq)

] +

+[ ]

[ ]


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II) Cation exchange

Organic acids (HL) can extract metallic cations (M+m) according to the

reaction:

mHLorg + M+maq → MLm org + mH+

aq (III)

The above equation describes a cation exchange reaction wherein hydrogen

ions are exchanged for the metal cation. Extractants which have been found useful

extracting metals by this mechanism are organic derivatives of phosphorous acids,

monocarboxylic acids and sulphonic acids etc.

e.g. The extraction of copper(II) with 1, 10-phenanthroline in chloroform from

hydrochloric acid media

Cu 2+ + o-phen [ Cu (phen) ]

[Cu (phen) ] + 2ClO4

_[Cu (phen)++ 2ClO4 ]

_

2+

2+

(aq)

(aq) (org)

(org) (org)

(org)

2. Extraction by Chelation

This mechanism is performed by acidic extractants that possess donor groups

capable of forming bidentate complex with metal ions. The equilibrium chemical

reaction describing the metal extraction is the same as that reported for cation

exchange system. Examples of chelating extractants β-diketones, oxine, cupferron

DMG etc.

e.g. Extraction of Al3+ from acetate medium with oxine

N

OAl

3

Oxine Al complex

3. Extraction by solvation

Solvating or neutral extractants (S) possess only donor groups that do not

contain dissociating protons, and because no anionic or cationic groups are available

in the molecule, the metal species are extracted from the aqueous phase as neutral


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complexes and the neutralizing ion as a water soluble negatively charged ligand (X-).

The extraction reaction can be written as:

ySorg + M+maq + mX-

aq → MXmSy org (IV)

As solvating extractants can be mentioned organic reagents containing oxygen

bonded to carbon, such as ethers, alcohols and ketones and those containing oxygen or

sulphur bonded to phosphorus as phosphoric esters, phosphonic oxides and

phosphonic sulphides.

e.g. Extraction of iron(III) by diethyl ether from 6 M HCl medium

]

]

FeCl3 + HCl [FeCl4-

H+

]

FeCl4-

H+

H2O+ [ H3O+

FeCl4-

[ H3O FeCl4+ -

+ ether [H+

(ether) FeCl4- (ether)]

4. Synergistic extraction

In this class there is an enhancement in the extraction by the use of two

extractants. The synergic extraction involved two steps. In first step metal ion reacts

with anionic ligand to form neutral complex. Where the positive charge on the metal

ion is neutralized by anion. At the same time equal numbers of water molecules are

removed by the negatively charged ligands depending upon number of bonding sites

from the coordination sphere of metal ion.

In the second step, neutral ligand react with uncharged complex and equal or

nearly all the remaining water molecule are removed from coordination sphere of

metal complex and finally there is formation of adduct [UO2(TTA)2TBP]

e.g. The extraction of uranium with tributyiphosphate (TBP) as well as 2-

thenoyltrifluoroacetate (TTA).Although either TBP or TTA are individually capable

of extracting uranium, if a mixture of these two extractants is used we get enhanced

extraction.

SC

H2C C CF3

OOS

C CH

C CF3

OHO

Keto TTA enol HTTA


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SC C

HC CF3

OHOS

C CH

C CF3

O-O

HTTA TTA-

+ H+

SC C

HC CF3

O-O

[UO2(H2O)4]2+ + 2

TTA-

[UO2(H2O)(TTA)2]

[UO2(H2O)(TTA)2] + U

O

O

O

TBP

O

O

C CH

C

O

C4H3S+ H2OTBP

CF3

C

CF3

HC

C

C4H3S

Techniques in Extraction [22]:

1. Choice of solvent:

Perhaps the most important consideration is the selection of solvent for use in a

particular extraction procedure is the extractability of the element of interest. A

consideration of the solubility of the solute in a particular solvent, the ease of recovery

of the solute from the solvent is important for subsequent analytical processing. The

boiling point of the solvent or the ease of the stripping by chemical reagents into

selection of solvent when the possibility of a choice exists. Similarly, the degree of

miscibility of the two phases, the relative specific gravities, viscosities, and tendency

to form emulsions should be considered. From the point of view of safety, the toxicity

and the flammability of the organic solvent obviously enter into the choice.

2. Stripping:

Stripping is the removal of the extracted solute from the organic phase for further

analysis. In many colorimetric procedures the concentration of solute of interest is

determined directly in the organic phase. However, the other conventional methods of

estimation are to be employed or further separation steps are required, to remove the

solute from the organic phase to a suitable medium. Depending on the volatility of the

organic solvent, the simplest procedure is to add a small volume of water to the extract

to hold the solute and to evaporate the volatile solvent on a steam bath. The addition


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of acid to the water before evaporation of volatile solvents in which chelate complexes

are dissolved helps to break the complex, thereby causing the metal ion to enter the

water solution. Sulphuric acid, nitric acid and perchloric acid were some times used to

destroy the residual organic matter.

Majority of the times, it is necessary to strip the solute from the solvent by

chemical means. The usual procedure being to shale the solvent with a volume of

water containing acids or other regents under optimum conditions whereby extractable

complex is separated. Thus metal ions are then quantitatively back extracted into the

stripping aqueous phase.

3. Backwashing:

An auxiliary technique used with batch extractions to effect quantitative

separation of elements is that of back washing. The combined organic phases after

several extractions contains practically some of the impurities and all the elements that

have been extracted to a much smaller extent depending on their relative distribution

ratios. This combined organic phase, when shaken with one or more small portions of

fresh aqueous phase containing the optimum reagent conc., salting out reagent etc.,

will result in a redistribution of the impurities, as well as of the major component,

between two phases. The bulk of the impurities, however, will be back-extracted to

the fresh aqueous phase, since their distribution ratios are much smaller.

4. Treatment of emulsion:

Mixing or agitating certain combinations of immiscible liquids, an emulsion

may result whereby one liquid is dispersed in a continuum of the other. The stability

or permanence of the dispersion is its most important property since it is necessary to

separate the phases for further steps in the analytical procedure. For an emulsion to

break or separate into its phases, both sedimentation and coalescence of the droplets of

the dispersed phase must occur.

The presence of a small amount of a solid phase at the interface often prevents

coalescence of emulsions, and filtration of both phases serves to prevent trouble.

Another method for reducing the tendency for emulsification is the addition of neutral

salts, which possibly increase the surface tension or the density. Another way of


Page | 38

avoiding emulsification is to allow only a small amount of the aqueous solution to

come in contact with a relatively large amount of the original solvent.

5. Variation of oxidation state:

Modification of the oxidation states of some of the ions present in solution, so

as to prevent the formation of metal complex necessary for extraction e.g. by reducing

iron(III) to iron(II) which does not extract, the extraction of iron from chloride

solution was prevented. Conversely for complete extraction of element proper

adjustment of valence state is required. These variations in oxidation state are

accomplished by the addition of the appropriate oxidizing or reducing agent.

6. Use of masking agents:

Masking agents are themselves metal-complexing agents. Which serve to

prevent particular metals from taking part in their usual reactions and thus remove

their interference without the necessity of an actual separation. In solvent extraction,

masking agents are used to prevent certain metals from forming extractable complex

and thus to greatly increase the selectivity of the extraction method in which masking

is employed. Masking was carried out by cyanide, tartrate, citrate, fluoride and EDTA

e.g. nickel may be extracted with dimethylglyoxime in the presence of cobalt if

cyanide is first used to mask the cobalt.

7. Use of salting out agents:

The term salting out agent is applied to those electrolytes whose addition

greatly enhances the extractability of complexes. The function of salting out agent

would be primarily of providing a higher concentration of complexing anion which,

by mass action would increase the concentration of complex and thus improve the

extraction. Water is probably bound as a shell of oriented water dipoles around the

ion and thus becoming unavailable as “free solvent”. Addition of salting out agents

decreases the dielectric constant of the aqueous phase, which favours the formation

of the ion association complexes.

Salting-out agents have been used with great success in separation involving

the halide and thiocyanate system.


Page | 39

Methods of extraction:

In most situations encountered in analytical chemistry the technique of liquid-

liquid extraction is employed to separate the solute of interest from substances that

interfere in the ultimate quantitative determination of the material. Most of the

analytical separations involving extraction are based on the favorable separation

factor, the extractions in which the separation factor approaches unity, it is necessary

to employ fractionation methods in which transfer, recombination and distribution of

various fractions are performed a sufficient number of times to achieve separation

[28].

Analytical chemistry, three basic types of solvent extractions are generally

utilized namely, I) batch extraction, II) continuous extraction and III) continuous

countercurrent extraction.

I. Batch extraction:

The method in which the volumes of solution as well as the volume of solvent

are contacted until equilibrium is attained and the two layers are then separated. This

is very simple extraction method used for the analytical separations. It is also used to

study the unknown systems and designed to yield the quantitative distribution

information.

If distribution ratio is not already known, it may be obtained by equilibrating

equal volume of the solution and extracting solvent. Batch extraction may be used to

advantage when the distribution ratio is large.

II. Continuous extraction:

When the distribution ratio is relatively small continuous extractions are

particularly applicable, so that to effect quantitative separation a large number of

batch extractions would normally be necessary. The continuous extraction device

operates on the principle, which consists of distilling the extracting solvent from a

boiler flask and condensing it and passing it continuously through the solution being

extracted. The efficiency of continuous extraction depends on the viscosity of the

phases, the values of distribution ratio, and the relative volumes of two phases.

The efficiency of continuous extraction processes may be conveniently evaluated

by a method devised by Bewick, Currah, and Beamishm [29] Continuous extraction


Page | 40

can conveniently be arranged according to whether the solvent is lighter than or

heavier than the phase being extracted.

III. Continuous countercurrent extraction:

This type of extraction involves a process whereby the two liquid phases are

caused to flow counter to each other. It is used to great advantage for separating

material for isolating or purification purpose, and it is also used extensively in

engineering problems.

Solvent extraction plays very crucial role in analytical chemistry and was

proved by number of research articles. The various techniques of solvent extraction

was introduced by Morrison and Freiser [22], Marcus and Kertus [6], Sekin and

Hasegava [23], Starry [25], Hanson [26].


Page | 41

References:

[1] F. W. Foiled, D. Kealey, Principals and Practice of Analytical Chemistry,

International textbook Company limited, 450 Edgware Rd., London W2 IEG

1975.

[2] A. K. De, S. M. Khopkar, R. A. Chalmers, Solvent Extractions of Metals, Van

Nostrand, Reinhold Co., London (1970).

[3] R. A. Day Jr., A. L. Underwood, Quantitative analysis, 6th ed, Prentice-Hall,

Inc., Englewood Cliffs, N. J., USA., 1-2 (1998) 462.

[4] H. A. C. McKay, Proceedings of the International Solvent Extraction

Conference, McMillan, London (1963).

[5] D. Dyrssen, Proceedings of the International Solvent Extraction Conference,

Gothenburg (1966), North-Holland Publishing Co., Amsterdam (1967).

[6] Y. Marcus, A. S. Kertes, Proceedings of the International Solvent Extraction

Conference, Jerusalem (1968), Wiley, Interscience, NewYork (1969).

[7] J. G. Gregory, Proceedings of the International Solvent Extraction Conference,

Hague (1971), Society of Chemical Industry, London,(1971).

[8] C. V. Jeffreys, Proceedings of the International Solvent Extraction Conference,

Lyon (1974).

[9] M. I. H. Baird, Proceedings of the International Solvent Extraction Conference,

Toronto (1977). Canadian Institute of Mining and METALLURGY, Society of

Chemical Industry, (1977).

[10] G. Duyckaertes, Proceedings of the International Solvent Extraction

Conference, Liege, Belgium (1980).

[11] J. C. King, Proceedings of the International Solvent Extraction Conference,

Denver, U.S.A. (1983).

[12] E. Blab, W. Nish, Proceedings of the International Solvent Extraction

Conference, Munich (1986).

[13] Y. A. Zolotov, Proceedings of the International Solvent Extraction Conference,

Moscow, USSR (1988).

[14] T. Sekine, Proceedings of the International Solvent Extraction Conference,

Kyoto-Japan (1990).


Page | 42

[15] Proceedings of the International Solvent Extraction Conference, York (1993).

[16] Proceedings of the International Solvent Extraction Conference, Melbourne

(1996).

[17] Proceedings of the International Solvent Extraction Conference, London

(1999).

[18] Proceedings of the International Solvent Extraction Conference, South Africa

(2002).

[19] Proceedings of the International Solvent Extraction Conference, Beijing, China

(2005).

[20] Proceedings of the International Solvent Extraction Conference, Tuscon, U. S.

(2008).

[21] Proceedings of the International Solvent Extraction Conference, Sangiago,

Chile (2011).

[22] G. H. Morrison, H. Freiser, Solvent Extraction in Analytical Chemistry, John

Wiley and sons, Inc., London, (1966).

[23] T. Sekine, Y. Hasegawa, Solvent Extraction Chemistry, Marcel Dekkar Inc.,

New York (1977).

[24] L. Alders, Liquid-Liquid Extraction, Elsevier, Amsterdam (1959).

[25] J. Starry, The Solvent Extraction of Metal Chelates, Pergamon, London (1964).

[26] C. Hanson, Recent Advances in Liquid-Liquid Extractions, Pergamon, London

(1971).

[27] Y. Marcus, A. S. Kertes, Ion Exchange and Solvent Extraction of Metal

Complexes, Wiley, Interscience, New York (1969).

[28] L. C. Craig, D. Craig, Techniques of organic chemistry, edited by A.

Weissberger, Vol. III, Part I, second edition, Interscience Publishers, Inc., New

York, (1956).

[29] H. A. Bewick, J. E. Currah, F. E. Beamish, Anal. Chem., 21 (1949) 1325.


Page | 43

Chapter II

4-Heptylaminopyridine: Synthesis and

characterization


Page | 44

2.1 Solvent extraction by high molecular weight amines

In analytical chemistry, nuclear industry, hydrometallurgy [1], mining industry,

etc high molecular weight amines have been widely used as liquid ion-exchanger for

the purification and recovery of various metal species by means of solvent extraction

[2]. High molecular weight primary, secondary and tertiary amines that are

organophilic weak bases which are used for solvent extraction of anionic species in

acidic aqueous solution. The interaction of these extractants with the anionic species

due to electrostatic force of attraction this sense as the ion-pair forming extractant.

These high molecular weight amines can be regarded as ‘liquid anion-exchangers’ in

the same way as the alkyl phosphoric acids can be regarded as ‘liquid cation-

exchangers’. This is because the extraction equilibria can at least formally, be

expressed by an ion-exchange reaction of anionic metal complex in the aqueous phase

with ligand anions combined with the extractant in the organic phase. Since the

extraction proceeds via formation of ion-pair, it depends on the charge and the ionic

size, and no specificity can be expected among anions of the same charge and size. As

the extractants forms variety of complexes with thiocyanate, nitrate, sulphate, halide

and number of other inorganic and organic anions it is used specifically for the

separation of many metal ions.

The primary, secondary and tertiary amines are the organic derivatives of

ammonia used for the extraction of metal ions, by anion exchange reaction with metal

anionic complex. These three types of amines acts as weak bases in aqueous phase;

can accept one proton and form anionic salt, while quaternary ammonium ions do not

require protonation before they can react. The lower molecular weight amines are very

soluble in water, due to this for solvent extraction high molecular weight amines are

preferred.

The basicity of primary or secondary amines in aqueous solution is not greatly

affected by the chain length. However, that of tertiary amines increases as the

molecular weight increases [3, 4]. The basicity of secondary amines in aqueous

solution is somewhat higher than primary or tertiary amines. The basicity of these

three classes of amines in organic solvent is different from that of aqueous solution

[5].


Page | 45

2.2 Solvent extraction of metals from organic acid solutions

It is important at this stage to consider the advantage of weak organic acid

medium over mineral acid medium. The different advantage of weak organic acid

media is the ease of adjustment of pH, the facility of controlling the concentration of

complexing ligand and the wide difference in pH at which various metals form

anionic complexes. Due to high stability of metal organic acid complexes, the organic

acid medium offered better separation of metals. The comparative study of back

extraction of complexes from the organic phase by fully exploiting the difference of

various metals to back extract in aqueous phase.

There are several general features which are essential for an extraction, if one has to

achieve the selective extraction of metals. These features are as follows:

The ability to extract the metal at desired acidity or pH.

To be selective for the required metal.

Ease of formation of complex with metal of interest and high solubility of

metal organic species in the organic phase.

Ease of recovery of the metal from organic phase.

It must be stable throughout the principle stage of solvent extraction.

It is to be prepared in laboratory on large scale.

To have acceptable rates of extraction and stripping.

Regeneration of extractant for recycling in economically large scale process.

Due to greater solubility in water, primary amines are used less frequently as

compared to secondary amine.

2.3 Extraction by ion-pair formation

The value of the ion-pair formation constant K is related to the dielectric constant (),

and temperature (T) by the expression

𝐾 =4𝜋𝑁𝑒2

1000∈𝐾𝑇Q (b),

Where, b = 𝑒2

𝑎∈𝐾𝑇

N = Avogadro’s number

e = Charge


Page | 46

K = Boltzmann constant

T = Absolute temperature

Q (b) = Calculable functions

a = Empirical parameter dependent upon the distance between charge centre of the

paired ions, when in contact.

Since the organic solvents used in extraction have a dielectric constant () less

than 40, ion association will be extensive in such solvents the decrease in the

dielectric constant of the aqueous phase by addition of salt favours ion-pair formation.

The effect of temperature on the value of K will depend on the temperature variation

of the dielectric constant. In solvents higher dielectric constants () deceases

markedly with temperature. So that T values fall with increasing T. In such solvents,

ion association increases with increasing temperature. In solvents of very low

dielectric constant, T increases with increase in temperature as the value of does

not change much, with the result that ion association falls off with rise in temperature

in solvents of this type.

According to Bjerrum equation [6] it is evident that ion association depends on

the value of ‘a’, decreasing with increasing ‘a’ values. If the value of ‘a’ does not

change appreciably with change in solvent, then the value of ion-pair constant (K) can

predicted in any solvent from its known value of ‘a’ in one solvent. It is fact that K

depends only on dielectric constant if ‘a’ and the temperature remains constant.

2.4 Common high molecular weight amines

Solvent extraction has emerged as one of the more popular separation

techniques because of its ease, simplicity speed, applicability both to trace and macro

level of metal ions. An organic solution of high molecular weight amines and amine

salts has been shown to be excellent extractants for metal ions from aqueous solution.

Smith and Page [7] reported that acid binding properties of high molecular weights

amines depends on the fact that acid salt of these bases are, in general, essentially

insoluble in water but readily soluble in organic solvent.


Page | 47

Primary amines are comparatively more water soluble than secondary and

tertiary amines and hence less frequently used for the extraction. Thus for the solvent

extraction of metal from aqueous medium secondary amines are used.

Extraction of many metal ions was carried out from organic acids,

monocarboxylic acid like salicylate, succinate and dicarboxylic acids like oxalic,

citric, tartaric, malonic. The extraction greatly depends on the nature, concentration of

amine and pH.

The most common high molecular weight amines used for the solvent

extraction studies are given in the table:

Table 1: Common high molecular weight amines

Amine Name Structure

Primary

n-Octylaniline

NH2

C8H17

Primene JMT H2N-C(R)(R’)(R”)

Octadecylamine CH3(CH2)17NH2

2-Octylaminopyridine

NNH-CH2

- (CH2)6- CH3

N-n-Octylaniline NH -CH2- (CH2)6 CH3

-

N-n-

Octylcyclohexylamine

(N-n-OCA)

NH (CH2)7- - CH3


Page | 48

Secondary N-n-

Decylaminopyridine

N

NH -(CH2)9 CH3-

Amberlite LA-1

[N-Dodecyl

(trialkylmethyl)amine]

HN

C(R) (R') (R'')

- CH2 C CH3- --

CH3 CH3

CH3CH3

CH2CH CHCH2C

Amberlite LA-2

[N-lauryl

(trialkylmethyl)amine]

HN

C(R) (R') (R'')

CH2(CH2)10CH3

N-n-Benzylaniline NH CH2

Tertiary

Tri-n-Dodecylamine

N-[CH2(CH2)10CH3]3

N-Methyl-Di-n-

Octylamine H3C

_ __ _(H2C)7

N

CH3

(CH2)7 CH3

Tri-n-Benzylamine

(TBA) N

Tri-octylamine (TOA) N-[(CH2)7CH3]3

Tri-iso-octylamine

(TIOA)

N-[C8H17]3

Aliquat 336 S


Page | 49

Quarternary

(Trialkylmethyl-

ammonium chloride)

[CH3-N-(CH2)7-11(CH3)3]+Cl-

Zephiramine

(Tetradecyldimethyl

benzyl ammonium

chloride)

H3C (CH2)13 N

CH3

CH3

+

Cl


Page | 50

2.5 4-Heptylaminopyridine (4-HAP) as an extractant

4-Heptylaminopyridine (4-HAP) as a novel extractant was prepared according

to the method reported by Singh, Kim and Lee [8] and used as an extractant. 4-

Heptylaminopyridine acts as secondary amine. In addition, the presence of heptyl

group renders this amine less soluble in water. There is no emulsion formation. It can

form ion-pair complex with metal ion easily. The extraction equilibria for ion-pair

formation can be expressed as,

[4-HAP] (org) + HA (aq) [4-HAPH+A-] (org) (1)

[4-HAPH+A-] (org) + B- (aq) [4-HAPH+B-] (org) + A- (aq) (2)

Where, A- = anion of weak organic acid

B- = metal-acid anionic complex

4-HAP = 4-Heptylaminopyridine

2.6.1 Synthesis of 4-Heptylaminopyridine (4-HAP)


sodium amide was added at 0oC and continued stirring for 30 min. The temperature of

the reaction mixture increased to room temperature and 1-bromoheptane was added

slowly. The reaction mixture was stirred at the ambient temperature for 1 h. The

reaction mixture was poured into water containing NH4Cl and extracted with

chloroform (150 mL). The chloroform extract was dried (Na2SO4) and evaporated on a

rotary evaporator to yield a residue which was crystallized to afford the corresponding

4-heptylaminopyridine.

N

NH2

+ NaNH2

N

NH

+ NH3

Na

THF/ Stirr

0 oC


Page | 51

+

N

NH Na

StirrBr-CH2-(CH2)5-CH3

1 hr.

N

NH-CH2-(CH2)5-CH3

+ NaBr

4-Heptylaminopyridine is white solid, which is readily soluble in xylene, toluene,

benzene, carbon tetrachloride, chloroform and acetone. Recrystallisation involves

huge losses. We recrystallised 4-HAP from acetone and obtained a product containing

99.9% of the main component. The yield was 75-85%. The purity was checked by

TLC and melting point was 44± 0.50C.

2.6.2 Characterization

a) IR spectrum

The IR spectrum of 4-heptylaminopyridine (Fig. 1) showed absorption band at

3427 cm-1 due to presence of –NH while at 1646 and 1545 cm-1 indicated presence of

carbon-nitrogen and carbon-carbon double bond respectively.

IR: 3427 (-NH (S)), 3052 (-CH, Ar.), 2957-2855 (-CH (S) (aliph.)), 1646 (-C=N (S)),

1545 (C=C) cm-1.

b) NMR Spectrum

Proton resonance assignments for the pure product were made using TMS as an

internal standard and chemical shift expressed in values, PMR (CDCl3, 300 MHZ,

Fig. 2).

NMR: CDCl3 (300 MHZ): , 0.851 (3H, t, -CH3); 1.61-1.81 (2H, m, -CH2); 2.4 (2H,

qn, -CH2); 3.23 (2H, qn, -CH2); 3.42 (2H, qn, -CH2); 4.35 (2H, qn, -CH2); 4.81 (2H, q,

-CH2); 6.5 (1H, S, -NH); 6.8-8.4 (4H, m, Ar-H) ppm.


Page | 52

The molecular structure of 4-Heptylaminopyridine is given as below,

N

NH-CH2-CH2-CH2-CH2-CH2-CH2-CH3


Page | 53

Fig. 1 IR Spectrum of 4-HAP


Page | 54

Fig. 2 NMR Spectrum of 4-HAP


Page | 55

References:

[1] E. Hogfeldt, S. Alegret, Ed., Ellis Horwood Chichester, UK, (1988) p. 36.

[2] B. C. Bhatta, S. Mishra, Int. J. of Non. Met., 3 (2014) 9.

[3] J. Clark, D. D. Perrin, Quart. Rev. (London), 18 (1964) 295.

[4] H. K. Hall, J. Am. Chem. Soc., 79 (1957) 5441.

[5] A. Rieure, M. Pumeau, B. Tremillon, Bull. Soc. Chim., Fr. (1964) 1053.

[6] N. Bjerrum, Kgl. Danske Videnskab. Selskab Mat. fys. Medd., 7 (1926) 9.

[7] E. L. Smith, L. E. Page, J. Soc. Chem. Ind., (London) 67 (1948) 48.

[8] O. M. Singh, S. J. Singh, S. N. Kim, S. G. Lee, Bull. Korean Chem. Soc., 28

(2007) 115.


Page | 56

Chapter III

Development of a solvent extraction system

with 4-heptylaminopyridine for the selective

separation of palladium(II) from synthetic

mixtures, catalysts and water samples


Page | 57

3.1 Introduction

Platinum group metals (PGMs) are of great practical importance and they have

a wide range of industrial applications, e.g. as catalysts in organic processes, value-

added components in metal alloys and the vehicle catalytic converter system. They are

used in the chemical, pharmaceutical, petroleum, electronic industries, and jewelry

making. These wide applications of PGMs, especially palladium(II), have increased

the palladium demand by 3.5% in 2007 to a total of 6.84 million ounces, whereas the

natural resources are limited [1, 2]. The use of palladium and platinum as catalyst in

the catalytic converters of cars and their eventual spread in the environment and also

the accumulation in wastewater by rain intensified environmental concerns. Since

palladium has no known biological role, all palladium compounds should be regarded

as highly toxic [3] similarly, palladium(II) can bind to thiol containing amino acids,

proteins, DNA, and several biomolecules and adversely affect the cellular processes

[4]. Therefore, the palladium(II) is strictly limited to be 5–10 ppm level by the

european agency for the evaluation of medicinal products [5]. The effective

palladium(II) extraction and recovery from both natural ore and industrial waste are

quite important from the viewpoint of full utilization of resources. Therefore, the most

important reasons for palladium(II) ions extraction, separation, and recovery are the

environmental concerns and economical impact.

Many analytical methods have been developed to determine the presence of

palladium(II) ions in clinical, environmental, industrial, and pharmaceutical samples

such as spectrophotometry, atomic absorption spectrometry, solid phase micro

extraction, high performance liquid chromatography, X-ray fluorescence,

electrochemical methods, Inductively Coupled Plasma-Atomic Emission

Spectrometry (ICP-AES) [6–11]. However, many of these are limited by

instrumentation cost, high training requirements, being cumbersome, time consuming

and unsuitable, especially in developing or less developed countries [12–14]. From the

viewpoint of analytical chemistry, there is increasing demand to develop reliable,

selective, sensitive methods to extract and separate the palladium(II) ions. Solvent

extraction also called liquid–liquid extraction is a process which allows separation of

two or more components, e.g. metal ions making use of their unequal solubilities in


Page | 58

two immiscible liquid phases. The solvent extraction is a suitable method for the

removal of PGMs from low concentrated sources, because it offers a number of

advantages like high selectivity and metal purity. Besides, more efficient removal of

metals is possible by the use of a multistage extraction.

3.2 Literature of the previously reported liquid-liquid extraction method for

palladium(II)

The fullerene black impregnated with trioctylamine was applied for the

extraction of palladium(II) from aqueous HCl medium [15]. The solvent extraction of

palladium(II) from aqueous chloride medium was carried out by N-benzoyl-N’, N’-

diethylthiourea [16]. Recovery of palladium(II) from spent catalysts was achieved

with Cyanex 921 from aqueous hydrochloric acid media by solvent extraction

technique [17]. In the solvent extraction of palladium(II) from chloride solution,

palladium(II) was extracted into Alamine 336 phase [18]. Extraction of palladium(II)

with Bis(2,4,4-trimethylpenty)phosphinodithioic acid from chloride solution has been

examined [19], palladium(II) was first selectively and quantitatively extracted into

chloroform. Palladium(II) was extracted from the aqueous solutions of their chloro

complexes using an N, N-dimethyldithiocarbamoylethoxy substituted calix [4] arene

[20].

The extractive separation of palladium(II) was analysed using a column packed

with divinylbenzene homopolymeric microcapsules containing tri-n-octylamine

(TOA) [21]. The proper selection of eluent helps the quantitative elution of

palladium(II) from column. 4-Alkylphenylamines had stronger interfacial activity so it

was effectively utilized as phase transfer catalyst to enhance the rate of extraction of

palladium(II) [22]. The extraction of palladium(II) with 1-[[2-(2,4-dichlorophenyl)-4-

propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole from HCl solutions has been

investigated [23]. The extraction complexes of palladium(II) by the novel ligands,

namely, N,N,N’,N’-tetra-(2-ethylhexyl) thiodiglycolamide (T(2EH)TDGA) and

N,N,N’,N’-tetra-(2-ethylhexyl) dithiodiglycolamide (DTDGA) [24] was determined

by extended X-ray absorption fine structure spectroscopy (EXAFS). The palladium(II)

ion, exhibiting 2 : 1 stoichiometry. Complex of palladium(II) and 2,2’-dithiodianiline

(DTDA) was extracted from an aqueous solution at pH 3 and determined by


Page | 59

spectrophotometric method [25]. Palladium(II) in synthetic mixtures, an alloy and

catalyst sample was successfully determined. Dicyclohexyl-18-crown-6 (DC18C6)

was used for the quantitative determination of palladium(II) from hydrochloric acid

and potassium thiocyanate media. Method was on the extraction and back-extraction

of palladium(II) has been developed [26]. Ketone derivative of calyx[4]arene was

used in nitrate medium for solvent extraction of palladium(II) [27]. Solvent extraction

method was developed for palladium(II) with 1-Benzoyl-3-[6-(3-benzoyl-thioureido)-

hexyl]-thiourea from nitric acid solutions [28]. N, N’–dimethyl-N, N’ –

diphenyltetradecylmalonamide (DMDPHTDMA) in 1, 2-dichloroethane was used for

the investigation of solvent extraction route for the separation of palladium(II) in

hydrochloric acid media [29]. Selective sorbent extraction of Pd(II) was carried out

and then separated as N, N-diethyl-N’-benzoylthiourea complex by an automated

column pre-concentration procedure [30]. Cyanex 923 was used for extraction and

separation of palladium(II) in chloride media at 4.0 – 5.0 M HCl [31]. Palladium(II)

was successfully stripped with 1:1 HCl + HClO4 in single step. Method was more

applicable by using SnCl2 as a labilising agent for the extraction of Pd(II).

Quantitative extraction and separation of Pd(II) from salicylate media using Aliquat

336 was studied [32]. Determination of extracted palladium(II) was carried out by

PAR method. Extraction of palladium(II) by bisacylated diethylenetriaminefrom

hydrochloric acid solutions was carried out [33]. N, N-Di(2-

ethylhexyl)aminomethylquinoline (DEQ) was used as the selective extractant for the

extraction of palladium(II) from the associated metal ions [34]. Pd(II) was selectively

extracted from precious metals and base metals from acidic chloride media has been

examined using theophylline derivatives [35]. Phosphonium ionic liquid:

trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) was used as a novel

reagent for extraction of palladium(II) from HCl medium [36]. The extraction was

very fast and efficient, nearly 98% of palladium(II) was quantitatively extracted.

The extraction of palladium(II) from hydrochloric acid solutions was carried out

with Aliquat 336 [37]. Palladium(II) can be extracted from aqueous medium to the

dichloromethane layer using quinoline-2-carboxalde- hyde 2-pyridylhydrazone [38].

Tin(II) chloride concentration was greatly influenced on the extraction of


Page | 60

palladium(II). Solvent extraction separation of palladium(II) was carried out with 2-

ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in toluene in the

presence of stannous chloride [39], 6 x 10-4 M PC-88A was enough for quantitative

extraction of Pd(II). The extraction behavior of base metals and precious metals from

aqueous chloride media was analyzed by a novel type of extractant p-(1, 1, 3, 3-

Tetramethylbutyl) phenyl hydrogen [N, N- di(2-ethylhexyl) aminomethyl phosphonate

[40]. This reagent has selectivity towards palladium(II) ions in the low acidic region.

The kinetics of palladium(II) extraction from chloride media with 1,2-bis(tert-

hexylthio)ethane were developed, the palladium complex was extracted with a

stoichiometry of 1: 1 [41]. 1-Octyltheobromine was utiliized to study extraction

equiliburium of palladium(II) from acidic chloride media [42]. Solvent extraction of

palladium(II) was studied involving ion-pairing of bromocomplexes of palladium(II)

with hexadecylpyridinium bromide (HDPB) [43]. The extraction reaction occurred

very effectively at the interface and thus the extraction rate was fast. Extraction of

palladium(II) ions using tri-n-octylamine xylene base supported liquid membranes

was carried in hydrochloric acid medium and stripping of palladium(II) was carried

out by agent like nitric acid [44]. Ionic liquids like trioctylammoniumbis

(trifluoromethanesulfonyl)amide ([TOAH][NTf2]) and trioctylammonium nitrate

([TOAH][NO3]) [45] were successfully implemented for extraction of palladium(II)

from 0.1 M HCl. Extraction of palladium(II) in the TRUEX and PUREX from nitric

acid solution by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide was

carried out effectively [46]. Macrocyclic endo-receptors in hydrochloric acid were

successfully applied for the solvent extraction of palladium(II) The DCH18C6 in

dichloroethane excellently extracted palladium(II) in the presence of KSCN [47].

Quantitative extraction of palladium(II) with thiacalix[4]arenes from nitric acid

nitrate–nitrite solutions method was developed and applied for the separation of

fission noble metals, including their heterometallic complexes [48].

Thiodiglycolamide was used for the rapid separation of palladium(II) in HCl solutions

[49]. Thiamacrocycles-synergized sulfonic acid extraction system was developed for

solvent extraction of palladium(II) in acidic nitrate solutions [50]. Di-(2-

ethylhexyl)thiophosphoric acid was used for selective extraction of palladium(II) as an


Page | 61

impregnated resins by adsorption of this extractant on Arnberlite XAD2 by means of a

dry impregnation method [51]. Palladium(II) was determined and separated by online

solid phase extraction by FIA-FAAS system. The method was successfully used for

determination of palladium in alloy and ore sample [52]. Palladium(II) was

determined from a pegmatite rock from Campo Largo County, Parana State, Brazil

and mineral veins of quartz by using [5-(4-dimethylaminebenzylidene)rhodanine] and

methyl isobutyl ketone at pH 2.4 [53]. Utility of alkane-1,ω-diyl bis(O,O-diisobutyl

phosphorodithioate)s (ADBDiBPDT) for the extraction of palladium(II) from precious

metals was carried out from 1.0 M chloride solution at pH 3 in 1,2-dichloroethane

through 1: 2 palladium(II) complex [54]. Carbon adsorbents like LKAU-4, LKAU-7

and BAU were studied for the extraction of palladium(II) from acidic medium [55]. 4-

Octylphenylamine, decyl isonicotiniate, decyl nicotiniate, decyl 2-hydroxyethyl

sulphide and its analog with partly fluorinated alkyl group were used for palladium(II)

extraction from 3M HCl [56]. Solid phase extraction (SPE) anion exchange cartridges

like Oasis MAX, Isolute SAX and Isolute NH2 was used commercially for the

separation of palladium(II) from aqueous chloride media [57]. The separation of

Pd(II) from the PGMs with HCl media was achieved by using trioctylamine (TOA)in

kerosene [58]. Solvent extraction of palladium(II) with various ketones in

nitrobenzene from nitric acid medium was investigated [59]. Methylalkylketones,

such as 2-octanone, 2-nonanone, 2-undecanone, 2-tridecanone, and ketones containing

symmetrical alkyl configuration, such as 5-nonanone, 5-decanone, 5-undecanone, and

6-undecanone exhibited significant extraction of palladium(II). The extraction

mechanism of Pd(II) from HNO3 or HCIO4 solution with N,N'-bis[l-phenyl-3-methyl-

5-hydroxypyrazole-4-benzylidenyl]-1,3-propylene diamine was studied [60].

Separation palladium(II) and platinum(IV) from the loaded Alamine 336 solution was

examined as a function of the concentration of stripping agents. Platinum group

metals are frequently used in the automobile catalysts, cancer therapy and space

material. Therefore their recovery has great importance hence solvent extraction of

palladium(II) was achieved from the HNO3, HCl and H2SO4 media by toluene solution

of Cyanex 923 [61]. The solvent extraction separation and recovery of Pd(II) from

HCl leach liquors of spent automobile catalyst employing precipitation and liquid-


Page | 62

liquid extraction methods was developed by tri-n-butyl phosphate (TBP) and Aliquat

336 [62]. Solvent extraction system with 1,2-bis(2-methoxyethylthio) benzene for the

selective separation of palladium(II) from secondary raw materials was developed

[63] and was further adopted for an industrial recovery of palladium(II) from

oxidising leach solutions gained from automotive catalysts. Palladium(II) was

extracted by bis(2-ethylhexy1) sulphoxide (BESO) over a wide range of acidity, and

BESO was shown to have a strong extraction ability toward it [64]. Solvent extraction

of palladium(II) was investigated with N,N-dioctylglycine in toluene from acidic

aqueous chloride media [65]. The chloroform extraction of Pd(II) from H2SO4 in

presence of potassium ethyl xanthate has been studied and it was observed that

palladium(II) was completely extracted [66]. N,N,N',N ' -tetra-n-octylethylenediamine,

N,N-di-n-octyl-2-(aminomethyl)pyridine, Alamine 336, and Aliquat 336 dissolved in

isodecanol-benzene were used to extract palladium(II) from a chloride medium [67].

The extraction behavior of (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-

1-ylmethyl)-pentan-3-ol with respect to palladium(II) were studied, it was found that

palladium(II) was efficiently extracted by the reagent from 0.1–6 M HCl [68]. Di-(2-

ethylhexyl) thiophosphoric acid (DEHTPA) in kerosene was used for solvent

extraction of palladium(II) from HCl media. The back-extraction of palladium(II)

from organic phase by different stripping reagents [69]. The reagent 1-phenyl-3-

methyl-4-benzoyl-5-pyrazolone at 60C was developed the separation method of

palladium(II) in molten solvent extraction. It was observed that increase in

temperature favor the reaction [70].

N, N, N’, N’-tetrakis[2-pyridyl-methyl]-1,2-ethylenediamine (TPEN).

N,N,N’,N’- tetrakis[4-(2-butyloxy)- 2-pyridyl-methyl ]-1,2-ethylenediamine (TBPEN)

and N,N,N’,N’- tetrakis (2-quinolinylmethyl)-1,2-ethylenediamine (TQEN) was used

for solvent extraction of Pd(II) in the acidic medium [71]. Pd(II) was separated by

using by bulk liquid membranes during electrodialysis. Method showed that an

effective separation of palladium(II) was achieved in the presence of an excess of the

carrier [72]. Cloud point extraction (CPE) in association with thermal lens

spectrometry (TLS) developed for determination of palladium(II) by using Triton X-

114 [73]. The method of extraction was used for determination of palladium(II) in


Page | 63

water sample. Activated carbon was chemically modified with ethyl-3-(2-

aminoethylamino)-2-chlorobut-2-enoate was applied for selective solid-phase

extraction of trace palladium(II) [74].

There is no report on the extraction and separation of palladium(II) from

salicylate medium by 4-heptylaminopyridine (4-HAP). The superiority of presently

employed method was also compared with other reported methods (Table 1). The aim

of the present work is to develop a simple, efficient, and environmentally friendly

extraction process for the separation and recovery of palladium(II) from salicylate

medium. The effect of pertinent parameters including pH, weak organic acid

concentration, extractant concentration, time, diluents, stripping agents, and diverse

ions as well as binary and ternary separation on palladium(II) extraction have been

investigated to obtain the optimum extraction conditions.

Table 1 Literature of the previously reported solvent extraction method for Pd(II)

System Aqueous

Phase

Organic

Phase

Special Feature Ref.

Fullerene black/ trioctylamine HCl Toluene Fullerene black

impregnated

with

trioctylamine

effectively

recovers

palladium(II)

from HCl

15

N-Benzoyl-N’,N’-

diethylthiourea

NaCl Chloroform Stoichiometry

of complex

was 1: 2

16

Cyanex 921 HCl Toluene Separation of

Pd(II) from

platinum group

metals

Recovery of

palladium(II)

from spent

catalysts

17

Alamine 336 HCl Toluene Separation of

palladium(II)

and

platinum(IV)

18

Bis (2,4,4-trimethylpenty) - Chloroform The separation 19


Page | 64

phosphinodithioic acid of

palladium(II)

and

platinum(II)

based on the

kinetic effect is

proposed

Palladium(II)

selectively

extracted into

chloroform

N,N-Dimethyldithio-

carbamoylethoxy substituted

calix [ 4 ] arene

- Chloroform Effective

extractant for

transferring

palladium(II)

from an

aqueous to a

chloroform

phase

20

Tri-n-octylamine (TOA) HCl TOA

molecules act

on the

extraction of

precious metal

21

4-Alkylphenylamines HCl Benzene &

Toluene

Adsorb at the

hydrocarbon /

water interface

22

1-[2-(2,4-dichloro phenyl)-4-

propyl-1,3-dioxolan- 2-

ylmethyl] -1 H-1, 2, 4-triazole

HCl Toluene The extraction

follows the

anion-

exchange

mechanism

Extraction of

precious metals

was also

carried out

23

N,N,N’,N’-tetra-

(2-ethylhexyl)

thiodiglycolamide

(T(2EH)TDGA) N,N,N’,N’-

tetra-(2-ethylhexyl) dithio

diglycolamide (DTDGA)

0.1 M

HNO3

n-Dodecane Palladium(II)

ion exhibiting

2 : 1

stoichiometry

24

2,2’-Dithiodianiline (DTDA) pH =3.0 Iso-butyl

methyl

ketone

The tolerance

limit for many

cations and

anions have

been

determined in

synthetic

25


Page | 65

mixtures,

catalyst and

alloy samples.

Dicyclohexyl-18-crown-6

(DC18C6)

HCl Chloroform Extraction

based on ion-

pair formation

of

palladium(II)

thiocyanate

26

Calix[4]arene HNO3 Chloroform Selective

extraction of

palladium(II)

27

1-Benzoyl-

3-[6-(3-benzoyl-thioureido)-

hexyl]-thiourea

HNO3 1,2-

Dichloro-

ethane

The increasing

number of

thioamide

groups in the

molecule,

increases its

extraction

efficiency

towards

palladium(II).

28

N,N’-dimethyl-N,N’-

diphenyltetradecylmalonamide

(DMDPHTDMA)

HCl 1,2-

Dichloro-

ethane

Easily

separation of

palladium(II)

from base

metals

29

N,N-diethyl-N’-

benzoylthiourea

HNO3 Interference of

other elements

impairs the

determination

Alkaline and

earth alkaline

metals as well

as iron can be

separated

30

Cyanex 923 HCl

4-5 M

Toluene Palladium(II)

was stripped

with 1:1 HCl +

HClO4

Separation of

palladium(II)

from

platinum(IV)

was observed

31

Aliquat 336 Salicylate

pH = 5.0

Xylene Separation of

palladium(II)

from base

metals

32


Page | 66

Analysis of

catalyst and

Ore

Bisacylated

Diethylenetriamine

HCl Toluene Separated from

associate

ferrous and

base metals

33

N,N-Di(2-ethylhexyl) amino

methyl quiniline (DEQ)

HCl Toluene Palladium(II)

extracted as 1:

1 complex

34

7-Octyltheophylline HCl Ethanol 100%

Stripping of

palladium(II)

with 1M

ammonia

solution

35

Cyphos IL 101 HCl Toluene Very efficient

and fast

extractant

Stripping of

palladium(II)

from 0.5 M

ammonia

solution

36

Aliquat 336 HCl Thiourea is an

efficient

stripping

reagent for

palladium(II)

37

Quinoline-2-carboxalde- hyde

2-pyridyl-hydrazone

Dichloro-

methane

Ligand formed

1:1 complex

38

2-Ethylhexyl phosphonic

acid mono-2-ethylhexyl ester

(PC-88A)

0.7-2.0 M

HCl-

HClO4

Toluene Palladium(II)

and

Platinum(IV)

was

quantitatively

separated

Analysis of

palladium(II)

in real sample

39

p-(1,1,3,3-Tetramethyl butyl)

phenyl hydrogen [N,N-di(2-

ethylhexyl) amino methyl

phosphonate

Toluene The recovery

and

purification of

precious metals

from various

materials such

as scraps

40

1,2-Bis(tert-hexylthio) ethane HCl Toluene Palladium(II)

extracted as 1:1

41


Page | 67

t-BHTE

1-Octyltheobromine HCl Toluene Stripping of

palladium(II)

was performed

over 60% by

ammonia or

thiourea

42

Hexadecylpyridinium bromide

(HDPB)

HBr Chloroform Average

recovery of

palladium(II)

was 99% with

an RSD of

0.95%

43

Tri-n-octylamine (TOA) HCl Xylene HNO3 was

used as

stripping agent

44

Trioctyl ammonium

bis(trifluoro methane sulfonyl)

amide ([TOAH][NTf2])

HCl Back-extracted

from the ionic

liquid mixture

with nitric acid

solution

45

Octyl(phenyl)-N,N-

Diisobutylcarbamoyl

methylphosphine

oxide

HNO3 n-Dodecane Solvent

extraction was

demonstrated

by adding

oxalic acid.

46

Dibenzo-18-crown-6

(DB18C6) and cis-syncis-

dicyclohexyl -18-crown-6

(DCH18C6)

HCl Dichloro-

ethane Extraction of

palladium(II)

in the presence

of KSCN.

47

Calix[4]arene,

thiacalix[4]arenes

HNO3

pH = 3

Combined

extraction of

palladium(II)

and silver(I)

from alkaline

solutions

Selective

extraction of

palladium(II)

from fission

alloy

48

N,N’-dimethyl-N,N’-di-n-

octyl-thiodiglycolamide

(MOTDA)

HCl n- Dodecane

& 2-ethyl-

hexanol

Nearly 100%

palladium(II)

was extracted

with MOTDA

49

Dinonyl naphthalene sulfonic

acid (HDNNS)

HON3 Kerosene

&

Dodecane

The influence

of the

concentration

of nitric acid,

50


Page | 68

HDNNS, and

thiamacrocycle

were studied

Di-(2-ethylhexyl)

thiophosphoric acid

(DEHTPA)

HCl n-Hexane Distribution

was studied

between

aqueous and

resin phase

51

4-(n-octyl)diethylene triamine HCl Metals

recovered were

quantitatively

eluted with 1

M HCl solution

52

[5-(4-dimethyl

aminebenzylidene) rhodanine

pH = 2.4 Isobutyl

ketone

Stripping was

performed with

3.0 M

sulphuric acid.

53

Alkane-1, ω-diyl Bis(O,O-

Diisobutyl

phiosphorodithioate)s

(ADBDiBPDT)

pH = 3.0 1,2-

Dichloro

ethane

Extraction 1: 2

or 1: 1

stoichiometry

was observed

54

LKAU-4, LKAU-7, and BAU HCl More than 60%

palladium(II)

was recovered

55

4-Octylphenylamine HCl 3.0M Toluene Extraction rate

increases with

ester

56

Isolute-SAX, OASIS-MAX,

Isolute-NH2

NaCl Extraction

efficiency

higher than

95%

57

Trioctylamine (TOA) HCI Kerosene Selective

transport; and

recovery of

platinum group

metals

58

2-Tridecanone HNO3 Nitro-

benzene Organic phase

was back

extracted with

thiourea

59

N,N'-bis[l-phenyl-3-methyl-5-

hydroxypyrazole-

4-benzylidenyl]-1,3-propylene

diamine (H,A)

HNO3

HCIO4

Chloroform

& Toluene

Distribution

ratio decreases

with acidity

and chloride

ion

concentration

60

Cyanex 923 HNO3 Toluene Palladium(II)

recovered from

spent


Page | 69

commercial

materials.

Mutual

separation of

palladium(II),

platinum(IV),

rhodium(III)

and associated

metal ions

61

Tri-n-butyl phosphate (TBP) HCl Kerosene Selective

separation of

palladium(II)

from other

metals

Separation and

recovery of

palladium(II)

from spent

automobile

catalyst

62

1,2-Bis(2-methoxyethylthio)-

benzene

1,2-

Dichloro-

benzene

Extract more

than 98% of

the

palladium(II)

0.5M thiourea

in 0.1 M

hydrochloric

acid used as

strippant

63

Bis(Zethylhexy1) sulphoxide

(BBSO)

HNO3

8 M

Toluene The high

extraction for

palladium(II)

recovery

64

N,N-dioctylglycine HCl/

NaCl

Toluene Extracted as a

1:2 metal:

reagent

65

Potassium ethyl xanthate H2SO4

10 M

Chloroform Extraction of

various

elements as

ethyl xanthate

complexes

from H2SO4

and HCl

66

Alamine 336, and Aliquat 336 pH Isodecanol-

benzene

Diamine

extractants

were superior

to a

monoamine

extractant for

67


Page | 70

the extraction

of

palladium(II)

(RS)-1-(4-chlorophenyl)-4,4-

dimethyl-3-(1H-1,2,4-triazol-

1-yl-methyl)-pentan-3-ol

HCl

0.1–6.0M

Chloroform Selective

separation of

palladium(II)

and copper(II)

from Fe(III),

Co(II) and

Ni(II)

68

Di-(2-ethylhexyl)

thiophosphoric acid

(DEHTPA or HL

HCl Kerosene Selective for

palladium(II)

against Fe(III),

Zn(II), Cu(II),

Pt(IV) and

Rh(III)

69

1-Phenyl-3-methyl-4-

benzoyl-5-pyrazone (PMBP)

pH = 1.0-

3.5

Paraffin

wax

The extraction

efficiency was

up to 97%

70

N,N’,N’-tetrakis[2-pyridyl-

methyl]-1,2-

ethylenediamine

pH = 1 Exhibited

selective

extraction of

palladium(II)

71

Diphenylthiourea/c di-o-

tolylthiourea

1,2-

Dichloro-

ethane

Effective

separation of

platinum(IV)

from

palladium(II)

was achieved

72

Triton X-114 pH = 4.0 Determination

of trace

amounts of

Pd(II) in spiked

water sample

73

Ethyl-3-(2-aminoethylamino)-

2-chlorobut-2-enoate

pH = 1 Many common

ions do not

interfere

The method was

validated for

determination of

ions in actual

samples

74


Page | 71

3.3 Experimental

3.3.1 Apparatus

UV/VIS Spectrophotometer model-Optizen α (mecasys Co., Ltd/made in South

Korea) with 1cm quartz cell was used for absorbance measurements and pH

measurements were carried out with an Elico Digital pH meter Model LI-120 with a

combined glass electrode.

3.3.2 Reagents

A Stock solution of palladium(II) was prepared by dissolving appropriate

amounts of analytical grade Palladium chloride hydrate (Johnson Matthey, UK) in

analar hydrochloric acid (1 M) and diluting to 250 mL with distilled water. 4-

Heptylaminopyridine was synthesized by reacting 4-aminopyridine with 1-

bromoheptane in the presence of base Sodium amide (NaNH2) in dry THF [75] and its

solutions were prepared in xylene. All the chemicals used were of analytical reagent

grade, were supplied from sigma (St. Loius, Mo, USA). Doubly distilled water was

used throughout.

3.3.3 Solvent extraction procedure








3.4 Results and discussion

3.4.1 Influence of pH on the extraction of palladium(II)

The effect of the pH in the range 0.1–10 on the extraction of palladium(II) was

carried out using 0.05 M 4-HAP in xylene. The amount of palladium(II) taken is 200

μg and aqueous–organic volume ratio of 2.5:1 was maintained. As can be seen in (Fig.

1), as the pH increases from 0.3 to 1.0, the percentage extraction increases. As the pH

increases above 1.0, the percentage of extraction decreases. This is because of the ion-


Page | 72

pair complex may be less stable at higher pH. Therefore, pH 0.5 was selected for the

further study (Table 2).

3.4.2 Effect of 4-HAP concentration on the extraction of palladium(II)

The extraction behavior of palladium(II) was studied with an extractant 4-HAP

concentration range of 0.01–0.15 M, at a pH of 0.5, and with 0.04 M sodium

salicylate. The quantitative extraction of palladium(II) was achieved in the

concentration range of 0.04–0.07 M 4-HAP (Table 3). Further increase in

concentration of 4-HAP, there was decrease in percentage extraction of palladium(II),

this is because of formation of stable RR’NH2+sal- species in which sal- will not be

replaced by Pd(sal)3- species. In order to ensure the complete extraction of

palladium(II) from the aqueous phase, 0.05 M 4-HAP is recommended for the general

extraction procedure (Fig. 2).

3.4.3 Effect of organic acid concentration on the extraction of Pd(II)

The extraction of 200 μg of palladium(II) was carried out from different weak

carboxylic acids like sodium succinate, sodium malonate, sodium ascorbate, and

sodium salicylate at pH 0.5 and 0.05 M 4-HAP in xylene. It is apparent from the

(Table 4) that the extraction of palladium(II) reaches maximum (99.5%) with

salicylate media in the concentration 0.03–0.05 M. This showed that the ion-pair

complex of palladium(II) was found to be quantitative in salicylate media in the range

of 0.03–0.05 M. As the concentration of sodium salicylate increases above 0.05 M, the

percentage extraction of palladium(II) decreases. Therefore, 0.04 M sodium salicylate

was used for further extraction processes. The extraction was incomplete in sodium

succinate (70.2%), sodium malonate (62.2%), and sodium ascorbate (28.5%) due to

the lack of ion-pair formation (Fig. 3).

3.4.4 Effect of diluents on the extraction of palladium(II)

The 200 μg of palladium(II) in 0.04 M sodium salicylate at pH 0.5 was

contacted with 10 mL of 0.05 M 4-HAP dissolved in different diluents. (Table 5)

showed the percentage extraction of palladium(II) loaded 4-HAP in different diluents.

It was found that 0.05 M 4-HAP solution in carbon tetrachloride, amyl alcohol,

toluene, and xylene provides quantitative extraction of palladium(II). The extraction

of palladium(II) was found to be incomplete in methyl isobutyl ketone (88.5%), n-


Page | 73

butyl alcohol (60.0%), kerosene (48.5%), 1,2-dichloroethane (45.7%), and chloroform

(20.0%) (Fig. 4). Xylene was preferred as a diluent for further extraction procedures,

because it provides a quicker phase separation with high distribution of the ion-pair

complex.

3.4.5 Influence of contact time on extraction of Pd(II)

The effect of contact time on extraction of palladium(II) in 0.04 M sodium

salicylate medium at pH 0.5, keeping an aq:org ratio of 2.5:1 and a 4-HAP

concentration of 0.05 M was examined in the range of 5 s–30 min (Table 6). The

extraction was found to be quantitative over the period of 4 min (Fig. 5). But to ensure

the complete extraction of palladium(II), 5 min equilibration time was recommended.

3.4.6 Stripping of palladium(II) from the loaded organic phase

Stripping of palladium(II) was carried out using different stripping reagents.

Stripping is the reverse of extraction. When the extraction of metal is carried out from

acidic medium, then back extraction is generally possible from the basic medium in

order to dissociate the ion-pair complex. The most efficient stripping of palladium(II)

from loaded organic phase was achieved with 4–10 M ammonia and ammonia buffer

pH 10. Among these two, ammonia solution is more preferred than ammonia buffer

(pH 10) solution to evaporate the aqueous phase more easily. The results obtained for

various stripping reagents examined are presented in (Table 7).

3.4.7 Loading capacity of the 4-HAP

Loading capacity of 4-HAP in xylene was determined by contacting

palladium(II) in 0.04 M sodium salicylate at a fixed aqueous to organic phase ratio

2.5:1. After equilibrium and phase separation, the same organic phase was used again

for the extraction of fresh feed solution of definite amount concentration of

palladium(II) (Table 8). The extraction of palladium(II) repeated till no further

extraction was found in the organic phase. The concentration of palladium(II) in the

organic phase of 4-HAP was found to be 2 mg (Fig. 6).

3.4.8 Effect of aqueous to organic volume ratio

In order to obtain a reliable, reproducible results and for a high extraction

efficiency, the aqueous:organic volume ratio is an another important parameter in

liquid–liquid extraction. The results of contacting different volume ratios of aqueous


Page | 74

to organic phases have been studied. The results indicate that a preferred aqueous/

organic (A/O) phase ratio in this study was found to be 4:1 or less. This is evident

from the sharp increase in the separation efficiency as well as the distribution of

palladium(II) when the phase ratio (A/O) changed from 25:1 to 4:1. This may simply

be due to unavailability of reagent for the extraction at higher phase ratio, so a

crowding effect occurs at a low phase ratio. However, in the recommended procedure

the phase ratio is maintained at 2.5:1 so as to avoid the large consumption of sodium

salicylate (Table 9).

3.4.9 Mechanism of the ion-pair complex

Attempts were made to ascertain the nature of the extracted species using log

D–log C plots. The graphs of log D[Pd(II)] against log C[4-HAP] at a fixed sodium

salicylate concentration (0.04 M) were found to be linear, having slopes of 0.88 and

0.74 at pH 2 and 3, respectively (Fig. 7). Also, plots of log D[Pd(II)] against log

C[salicylate] at fixed 4-heptylaminopyridine concentration (0.05 M) were linear and the

slope values were found to be 2.70 and 2.75 at pH 3 and 4, respectively (Fig. 8). The

probable composition of the extracted species was calculated to be 1 : 3 : 1 (metal :

acid : extractant).

In the mechanism of extraction first step is protonation of 4-HAP to form the

cationic species as RR’NH2+ and second step is formation of anionic species by

combining salicylate with Pd(II) as [Pd(Sal)3]-aq and both of these cationic and anionic

species associate to form an ion-association of type [RR’NH2+Pd(Sal)3

-]org

I] Probable mechanism of extraction:

RR'NHorg + H+aq RR'NH2

+

PdCl2 aq + Cl-aq PdCl3

- aq

PdCl3-

aq+ 3Hsal aq

[Pd (sal)3]-

aq + 3H+

RR'NH2+

org + [Pd (sal)3]-

aq [RR'NH2+Pd (sal)3

-] org

II] Probable mechanism of stripping:

When organic phase was back stripped with 6.0 M NH3 solution, there is

formation of [Pd(NH3)2(H2O)2]2+ species in the stripped solution [77].


Page | 75

RR'NHorg [RR'NH2+Pd (sal)3

-] org+ 2NH4OH + [Pd(NH3)2(H2O)2]

2+aq

3 Salicylate-

aq+ + H+

3.5 Applications

3.5.1 Effect of diverse ions

In order to evaluate the suitability of the proposed method for extraction of

palladium(II), the effect of some diverse ions was studied by adding different amounts

of diverse ions to 200 µg of palladium(II) with 4-HAP (10 mL 0.05 M) in 0.04 M

sodium salicylate. An error less than ± 2% was considered to be tolerable (Table 10).

The selectivity of proposed method was enhanced by masking the tolerable cations

with a suitable masking agent.

3.5.2 Separation of palladium(II) from binary mixtures

The separation of palladium(II) from the associated metal ions has been

achieved under the optimum separation conditions in binary mixtures in binary

mixtures. At this condition palladium(II) is extracted quantitatively leaving Fe(III),

Ni(II), Co(II), Cu(II), Pt(IV), Os(VIII), Ir(III), Ru(III), Au(III), Rh(III), Hg(II), Zn(II),

Pb(II), Cd(II), Bi(III), Te(IV), and Ag(I) in the aqueous phase from which they are

determined spectrophotometrically by standard methods (Table 11). palladium(II)

from the organic phase was stripped and estimated spectrophotometrically by applying

dithizone method.

3.5.3 Separation of palladium(II) from ternary mixtures

palladium(II) selectively extracted from ternary mixtures. palladium(II) is one

of the platinum group metals (PGMs), and therefore, palladium(II) was separated from

Ag(I), Au(III); Ru(III), Rh(III); Ir(III), Pt(IV); Au(III), Pt(IV); and Os(VIII), Au(III).

In this case, the Os (VIII) is masked by the suitable masking agent (Table 12). All the

PGMs are not extracted with 10 mL 4-HAP in xylene at 0.04 M sodium salicylate and

pH 0.5. palladium(II) was also isolated from Cu(II), Co(II); Fe(III), Ag(I); Zn(II),

Cu(II); Ni(II), Co(II); Fe(III), Cu(II); and Se(IV), Te(IV).


Page | 76

3.5.4 Analysis of palladium(II) from a synthetic mixture corresponding to the

composition of alloy

To ascertain the selectivity of the proposed method, it was successfully applied

for the determination of palladium(II) in alloys from salicylate media at pH 0.5. The

real samples were not available; hence the synthetic mixtures were prepared

corresponding to the composition of the alloy. The results of the analysis are reported

in (Table 13).

3.5.5 Analysis of palladium(II) in catalyst

The proposed method is applicable for the determination of palladium(II) in

various catalysts. A known amount of the catalyst was dissolved in a mixture of 9 mL

and 3 mL of concentrated hydrochloric and nitric acid, respectively. The solution of

catalyst is then heated with concentrated hydrochloric acid to remove the oxides of

nitrogen. The residue was dissolved in 10 mL of 1.0 M hydrochloric acid and filtered

to remove carbon or barium sulfate. The residue was washed with dilute HCl. The

filtrate and washings were collected and diluted with water in a standard volumetric

flask. An aliquot of the sample solution was taken, and palladium(II) was determined

as per the general procedure. The results of the analysis are collected in (Table 14).

3.5.6 Determination of palladium(II) in different water samples

In order to investigate the accuracy and applicability of this method, real

samples were analyzed. For the sample preparation, 200 µg of palladium(II) were

spiked into the solutions and the results of recovery are shown in (Table 15).

3.6 Conclusions

The present investigations highlight that 4-Heptylaminopyridine is a useful

extractant for extraction of palladium(II) and also for their separation from

most of the commonly associated metal ions.

The separations can be accomplished at room temperature.

The stripping agent used for separation is simple and convenient for further

processing of solutions.


Page | 77

In the earlier methods employed for extraction of palladium(II) the medium

used is mineral acid, but in our proposed method we used a weak acid as a

medium for extraction, in that sense our method is greener than the earlier.

The developed conditions of extraction have been successfully extended to

recover palladium(II) from synthetic mixture, alloys, catalysts, water samples,

and binary and ternary metal ion mixtures.

The method developed for the extraction of palladium(II) is very simple,

selective, rapid, and cost effective for the separation and determination of

palladium(II).


Page | 78

Table 2 Effect of pH on the extraction of palladium(II)

Palladium(II) = 200 µg Aq. : Org. = 2.5:1

Org. = 0.05 M 4-HAP in xylene (10 mL) Sodium salicylate = 0.04 M

Strippant = 6.0 M Ammonia (2× 10 mL)

pH Percentage extraction, (% E) Distribution ratio, (D)

0.05 80.2 10.12

0.1 96.5 68.92

0.3 100 ∞

0.5* 100 ∞

0.7 100 ∞

1.0 100 ∞

1.5 85.1 14.27

1.7 80.0 10.0

2.0 79.4 9.63

3.0 62.8 4.22

4.0 56.5 3.24

5.0 42.8 1.87

6.0 43.1 1.89

7.0 28.5 0.99

8.0 22.8 0.73

9.0 8.57 0.23

10.0 8.57 0.23

*Recommended for general extraction procedure


Page | 79

Table 3 Effect of 4-HAP concentration on the extraction of palladium(II)

Palladium(II) = 200 µg pH = 0.5

Strippant = 6.0 M Ammonia (2× 10 mL) Sodium salicylate = 0.04 M

Aq.: Org. = 2.5: 1

4-HAP (M) Percentage extraction, (% E) Distribution ratio, (D)

0.01 41.7 1.78

0.02 73.4 6.90

0.03 95.1 48.94

0.04 100 ∞

0.05* 100 ∞

0.06 100 ∞

0.07 100 ∞

0.08 98.5 172.32

0.09 96.5 70.38

0.10 94.5 43.54

0.11 93.7 37.24

0.12 91.7 27.65

0.13 91.1 25.71

0.14 89.1 20.52

0.15 87.7 17.84

0.16 86.0 15.35



Page | 80

Table 4 Effect of organic acid concentration on the extraction of Pd(II)

Pd(II) = 200 µg pH = 0.5

Org. = 0.05 M 4-HAP in xylene (10 mL) Aq.: Org. = 2.5:1


Weak organic

acid

concentration,

(M)

Sodium salicylate Sodium

succinate

Sodium

malonate

Sodium

ascorbate

% Ea Db % Ea Db % Ea Db % Ea Db

0.005 52.0 2.70 37.7 1.51 45.4 2.07 24.0 0.78

0.01 66.0 4.85 39.1 1.60 46.8 2.19 24.8 0.82

0.02 88.2 18.68 58.0 3.45 60.2 3.78 32.2 1.18

0.03 95.7 55.63 70.2 5.88 60.2 3.78 25.1 0.83

0.035 100 ∞ 69.4 5.66 61.1 3.92 27.1 0.92

0.04* 100 ∞ 67.1 5.09 62.2 4.11 28.5 0.99

0.045 100 ∞ 65.7 4.78 61.4 3.97 27.7 0.95

0.05 100 ∞ 64.5 5.54 61.7 4.02 26.2 0.88

0.06 80.0 10 59.7 3.70 58.8 3.56 27.4 0.94

0.07 61.4 3.97 70.0 5.83 81.4 10.94 23.7 0.77

0.08 40.8 1.72 50.5 2.55 74.2 7.18 22.8 0.73

0.09 20.0 0.62 55.1 3.06 54.8 3.03 21.1 0.66

0.1 5.71 0.15 52.8 2.79 53.7 2.89 19.4 0.60

a = Percentage extraction, b = Distribution ratio



Page | 81

Table 5 Effect of diluents on the extraction of palladium(II)



Strippant = 6.0 M Ammonia (2× 10 mL) Aq.: Org. = 2.5:1

Solvents Dielectric constant Percentage

extraction, (%E)

Distribution ratio,

(D)

Xylene* 2.30 100 ∞

Toluene 2.38 100 ∞

Amyl alcohol 13.90 100 ∞

Carbon tetrachloride 2.24 100 ∞

Methyl isobutyl

ketone

13.11 88.5 19.23

n-Butyl alcohol 17.51 60.0 3.75

Kerosene 1.8 48.5 2.35

1,2-Dichloroethane 1.25 45.7 2.10

Chloroform 4.81 20.0 0.625



Page | 82

Table 6 Effect of contact time on the extraction of palladium(II)



Strippant = 6.0 M Ammonia (2× 10 mL) Aq.: Org. = 2.5:1

Contact time, min Percentage extraction, (% E) Distribution ratio, (D)

0.05 28.0 0.97

0.15 40.5 1.70

0.30 53.4 2.86

0.45 61.4 3.97

1 73.1 6.79

2 75.4 7.66

3 92.8 32.2

4 100 ∞

5* 100 ∞

6 100 ∞

7 100 ∞

8 100 ∞

9 100 ∞

10 100 ∞

15 100 ∞

20 70.0 5.83

25 34.2 1.29

30 30.0 1.07



Page | 83

Table 7 Stripping of palladium(II) from the loaded organic phase


Org. = 0.05 M 4-HAP in xylene (10 mL) Salicylate = 0.04 M

Aqueous : Organic = 2.5:1

Strippant,

M

Ammonia HCl Acetic acid H2SO4 NaOH

%Ea Db %Ea Db %Ea Db %Ea Db %Ea Db

1 52.5 2.76 18.8 0.57 5.14 0.13 5.42 0.14 12.5 0.35

2 68.8 5.51 40.2 1.68 6.85 0.18 5.71 0.15 13.1 0.37

3 87.1 16.86 48.0 2.30 9.71 0.26 7.14 0.19 14.2 0.41

4 100 ∞ 58.8 3.56 10.0 0.27 7.71 0.20

No Stripping

5 100 ∞ 64.8 4.60 9.42 0.25 4.28 0.11

6* 100 ∞ 70.5 5.97 12.2 0.34

No Stripping

7 100 ∞ 77.7 8.71 16.0 0.47

8 100 ∞ 80.5 10.32 17.1 0.51

9 100 ∞ 82.8 12.03 19.1 0.59

10 100 ∞ 84.8 13.94 20.8 0.65

aPercentage Extraction, (%E) bDistrbution ratio, (D)


%E D

Ammonia buffer (pH = 10) 100 ∞

Acetate buffer (pH = 4.7) 35.4 1.36

Water 10.2 0.28

HNO3 No Stripping


Page | 84

Table 8 Loading capacity of the 4-HAP

pH = 0.5

Org. = 0.05 M 4-HAP in xylene (10 mL) Salicylate = 0.04 M

Strippant = 6.0 M Ammonia (2× 10 mL) Aqueous : Organic = 2.5:1

Palladium(II), µg Percentage extraction, (% E) Distribution ratio, (D)

100 100 ∞

200* 100 ∞

400 100 ∞

800 100 ∞

1000 100 ∞

1500 100 ∞

2000 100 ∞

2400 95.7 55.63

3000 91.4 26.56

4000 87.1 16.87

5000 82.0 11.38



Page | 85

Table 9 Influence of aqueous to organic volume ratio on extraction of Pd(II)




Aq: Org Percentage extraction, (%

E)

Distribution ratio, (D)

10:10 100 ∞

20:10 100 ∞

25:10* 100 ∞

30:10 100 ∞

35:10 100 ∞

40:10 100 ∞

50:10 97.7 106.19

70:10 95.4 51.84

100:10 48.5 2.35

150:10 42.0 1.81

200:10 34.2 1.29

250:10 28.5 0.99



Page | 86

Table 10 Effect of diverse ions on the extraction of palladium(II)

Amount tolerated (mg) Diverse ion added

25 Te(IV)

15 Zn(II), Hg(II), chloride

10 Cu(II), Ni(II), Co(II), Cd(II), Bi(III), Sb(III), Mg(II), Sn(II),

Pb(II)b, bromide, citrate, nitrate

5 fluoride, malonate, acetate, oxalate

Cr(VI), Fe(III)a, Fe(II)a, Se(IV)a, Ca(II)c, In(III), Tl(I), U(VI)a

3 V(V)a, Au(III)e, Pt(IV)d, nitrate, succinate

2 tartarate, Ga(III)d, Os(VIII)f, Mo(II)d, W(VI)a, Ru(III)f, Rh(III)f

1 EDTA, sulphate, iodide

0 thiourea, thiosulphate, ascorbate

aMasked with 3 mg fluoride

bMasked with 3 mg acetate

cMasked with 7 mg citrate

dMasked with 3 mg oxalate

eMasked with 7 mg bromide

fMasked with 12 mg chloride


Page | 87

Table 11 Separation of palladium(II) from binary mixtures

Metal Ion Amount taken,

µg

Average

recovery (%)a

Chromogenic

ligand

Reference

Pd(II)

Fe(III)

200

60

99.8

98.5

Thiocyanate

76

Pd(II)

Ni(II)

200

40

99.3

99.7

DMG

76

Pd(II)

Co(II)

200

300

99.3

99.5

Thiocyanate

76

Pd(II)

Cu(II)

200

300

99.5

99.3

Cuproine

76

Pd(II)

Pt(IV)

200

300

99.3

99.6

Stannous chloride

76

Pd(II)

Os(VIII)b

200

300

99.3

99.6

Thiourea

78

Pd(II)

Ir(III)

200

80

99.9

99.7

Stannous chloride

hydrobromic acid

76

Pd(II)

Ru(III)

200

200

99.9

99.7

Thiourea

78

Pd(II)

Au(III)

200

200

99.8

98.9

Stannous chloride

78

Pd(II)

Rh(III)

200

200

98.8

99.5

Potassium iodide

76

Pd(II)

Hg(II)

200

100

99.8

98.4

PAN

79

Pd(II)

Zn(II)

200

60

99.9

99.2

PAR

79

Pd(II)

Pb(II)

200

100

99.9

99.0

PAR

76

Pd(II)

Cd(II)

200

10

99.8

98.9

PAR

79

Pd(II)

Bi(III)

200

300

99.9

99.0

Ascorbic acid +

Potassium iodide

76

Pd(II)

Te(IV)

200

120

99.7

99.4

Bismuthiol II

76

Pd(II)

Ag(I)

200

120

99.9

99.7

Rhodanine

76

aAverage of six determinations bMasked with 12 mg chloride


Page | 88

Table 12 Separation of palladium(II) from ternary mixtures

Composition of mixture

µg

Percentage recovery of

palladium(II) (% R)* RSD (%)

Pd(II) 200; Se(IV) 200; Te(IV) 120 99.2 0.66

Pd(II) 200; Fe(III) 60; Cu(II) 300 99.6 0.33

Pd(II) 200; Ni(II) 40; Co(II) 300 99.1 0.84

Pd(II) 200; Ag(I) 120; Au(III) 200 98.6 0.40

Pd(II) 200; Ru(III) 200; Rh(III) 200 99.3 0.67

Pd(II) 200; Ir(III) 80; Pt(IV) 300 99.9 0.04

Pd(II) 200; Zn(II) 60; Cu(II) 300 99.7 0.39

Pd(II) 200; Au(III) 200; Pt(IV) 300 99.6 0.45

Pd(II) 200; Fe(III) 60; Ag(I) 120 99.9 0.17

Pd(II) 200; Au(III) 200;

Os(VIII)a300

99.6 0.26

Pd(II) 200; Cu(II) 300; Co(II) 300 99.0 0.71

*Average of five determinations

aMasked with 12 mg chloride


Page | 89

Table 13 Analysis of palladium(II) in synthetic mixture corresponding to the

composition of alloy

Alloy Composition

(%)

palladium(II)

taken (µg)

Palladium(II)

Found (µg)

Relative

recoverya

(%)

RSD

(%)

White gold Au-75, Pd-10,

Ni-10, Zn-5

10 9.9 99.1 0.84

Jewellery alloy Pd-95.5, Ru-

4.5

95.5 95.1 99.7 0.17

Pd – Cu Pd-60, Cu-40 60 59.7 99.6 0.26

Stibio

palladinite

mineral

Pd-75, Sb-25 75 73.9 98.6 0.8

Oakay

i) Pd-10.5, Pt-

20, Ni-60, V-

9.5

10.5 10.4 99.6 0.45

ii) Pd-18.2,

Pt-18, Ni-54,

V-9.5

18.2 18.0 98.9 0.71

Dental alloy

i) Ag-45, Pd-

50,Pt-2, Au-1

50 49.7 99.5 0.56

ii) Ag-15, Au-

60, Pd-10, Pt-

15

10 9.9 99.8 0.09

iii) Pd-34, Ni-

34,Co-22,

Au-10

34 33.8 99.4 0.37

Solder alloy Pd-30, Pt-10,

Au-60

30 29.8 99.4 0.52

Golden colour

silver alloy

Pd-26, In-21,

Cu-18, Ag-35

26 25.8 99.5 0.49

Pd – Au Pd-50, Au-50 50 49.6 99.3 0.67

Autocatalyst Pd-20, Pt-15,

Rh-50

20 19.9 99.9 0.04

aAverage of five determinations


Page | 90

Table 14 Analysis of palladium(II) in catalyst

Catalyst Palladium(II)

added (µg)

Palladium(II)

found

by proposed

method (µg)

Relative

recoverya

(%)

RSD

(%)

Pd on BaSO4 (5%) 200 199.66 99.8 0.29

Pd on BaCO3 (5%) 200 199.80 99.9 0.06

Pd on CaCO3 (5%) 200 199.86 99.9 0.04

Pd on Carbon (10%) 200 199.40 99.7 0.33

Pd on Carbon (5%) 200 199.86 99.9 0.05


Table 15 Determination of palladium(II) in different water samples

Sample palladium(II)

spiked (µg)

palladium(II)

found (µg)

Relative

recoverya

(%)

RSD

(%)

Distilled water 0.00 n.f. - -

200 199.86 99.9 0.04

Tap water 0.00 n.f. - -

200 199.80 99.9 0.06

Waste water 0.00 n.f. - -

200 199.66 99.8 0.29

River water 0.00 n.f. - -

200 199.40 99.7 0.33

aAverage of five determinations n.f. = not found


Page | 91

Fig. 1 Effect of pH on the extraction of Pd(II)

Condition:

Pd(II) = 200 µg, salicylate = 0.04 M, 4-HAP = 0.05 M in xylene, aq. : org. volume ratio = 2.5

: 1, strippant = 6.0 M NH4OH (2 X 10 mL), shaking time = 5.0 min.


Page | 92

Fig. 2 Effect of 4-HAP concentration on the extraction of Pd(II)

Condition:

Pd(II) = 200 µg, salicylate = 0.04 M, pH = 0.5, aq. : org. volume ratio = 2.5 : 1, strippant =

6.0 M NH4OH (2 X 10 mL), shaking time = 5.0 min.


Page | 93

Fig. 3 Effect of organic acid on the extraction of Pd(II)

Condition:

Pd(II) = 200 µg, 4-HAP = 0.05 M in xylene (10 mL), pH = 0.5, shaking time = 5.0 min.,

strippant = 6.0 M NH4OH (2 X 10 mL), aq. : org. volume ratio = 2.5 : 1


Page | 94

Fig. 4 Effect of diluents on the extraction of Pd(II)

Condition:

Pd(II) = 200 µg, pH = 0.5, salicylate = 0.04 M, 4-HAP = 0.05 M in variable diluents (10 mL),

aq. : org. volume ratio = 2.5 : 1, shaking time = 5.0 min., strippant = 6.0 M NH4OH (2×10

mL)


Page | 95

Fig. 5 Effect of shaking time on the extraction of Pd(II)

Condition:

Pd(II) = 200 µg, pH = 0.5, salicylate = 0.04 M, 4-HAP = 0.05 M in xylene,

strippant = 6.0 M NH4OH (2×10 mL), aq. : org. volume ratio = 2.5 : 1


Page | 96

Fig. 6 Loading capacity of the 4-HAP

Conditions:

pH = 0.5, salicylate = 0.04 M, 4-HAP = 0.05 M in xylene, aq. : org. volume ratio = 2.5 : 1,

shaking time = 5.0 min., strippant = 6.0 M NH4OH (2×10 mL)


Page | 97

Fig. 7 log-log plot of distribution ratio Log D[Pd(II)] versus Log C[4-HAP] at fixed salicylate

concentration (0.04 M)

Conditions:

Pd(II) = 200 µg, salicylate = 0.04 M, shaking time = 5.0 min., pH = 2 and 3,



Page | 98

Fig. 8 log-log plot of distribution ratio Log D[Pd(II)] versus Log C[salicylate] at fixed

4-heptylaminopyridine concentration (0.05 M)

Conditions:

Pd(II) = 200 µg, pH = 3 and 4, shaking time = 5.0 min., 4-HAP = 0.05 M in xylene (10 mL),



Page | 99

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Page | 103

Chapter IV

Development of a solvent extraction

system with 4-heptylaminopyridine for

the selective separation of platinum(IV)

from catalysts, anticancer injections and

water samples


Page | 104

4.1 Introduction

Platinum is an element in the platinum group of metals (PGMs), which are

available in nature as an arsenite compound or in a sulfide associated with copper,

nickel, iron, etc. Platinum is employed in various industries, in electronics and

electrical devices, in catalysts, jewelry and dental materials, for the production of fuel

cells, for platings and coatings, and in glass making. As a catalyst, it is widely used in

the automobile, chemical and petrochemical industries. Secondary/waste materials

containing platinum are generated and discarded during production and at the end of

service life. To recover valuables from primary and secondary resources,

pyro/hydrometallurgical processes consisting of roasting and leaching are usually

employed to dissolve the metals into an aqueous phase using suitable lixiviants [1].

The consumption of platinum and palladium by the autocatalyst sector is rising by 5%

each year. As a consequence spent automobile catalysts have emerged as a major

secondary source of platinum and palladium [2].

Platinum demand in 2003/2004 was higher than the world supply [3]. Although

the demand decreased 2.3% in 2008, platinum supply decreased 4.2% [4].

Platinum metal is also very scarce element in earth’s crust. The worldwide reserves of

platinum metal are concentrated in only Siberia and South Africa. Although the

amount of this metal in a commercial catalyst is approximately1 wt.%, it corresponds

to the main cost of this product [5, 6]. Therefore, recycling of spent catalysts is an

attractive way to lower the catalyst cost [7]. Economically, the platinum group metals

are important as investment commodities and currency. Under ISO 4217 the

palladium, silver, platinum and gold are internationally recognized as forms of

currency [8]. Cisplatin, cis-diammine-dichloro-platinum(II), is an inorganic

coordination compound commonly used in the treatment of different solid tumors.

However, it is also highly toxic and probably carcinogenic to humans [9]. The

presence of cisplatin in water and wastewater has been reported. Excretion via faeces

and urine of patients under medical treatment, the disposal of unused pharmaceuticals

[10-12] in effluent from hospitals [13-16] and the wastewater generated during the

pharmaceutical manufacturing process [17] represent the major contamination sources

for this cytostatic drug.


Page | 105

4.2 Review of literature for solvent extractive separation of Pt(IV)

Solvent extraction of Pt(IV) from nitrate, chloride and sulfate solution has been

examined by using bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302)

[18] in kerosene and Cyanex 923 [19] in toluene from chloride media. From chloride

leach liquors of spent automobile catalyst [20] and platinum-191 radiotracer [21] the

platinum was extracted and separated with rubeanic acid (ethanedi-thioamide) in

tributyl phosphate was examined. N,N-diethyl-N'-benzoylthiourea (DEBT) [22] was

used to extract the Pt(IV) by optimizing the mole ratio of metal to chelating agent,

concentration of acid, extraction time and temperature. The solvent extraction of

Pt(IV) with bis(n-octylsulphinyl) ethane BOSE [23] was studied. Results showed that

platinum(IV) were not extracted from hydrochloric acid solution with BOSE into

butyl- acetate or chloroform but it could be extracted from 2 to 6 M HCl in the

presence of potassium iodide. p-(I,1,3,3-Tetramethylbutyl)phenyl hydrogen [N,N-

di(2- ethylhexyl)aminomethyl-phosphonate [24] was used as a novel extractant to

study the extraction behavior of platinum(IV) from aqueous chloride media. Solvent

extraction of platinum from chloride media has been carried out by using N,N'-

dimethyl-N,N'-diphenyltetradecylmalonamide [25]. Platinum can be quantitatively

extracted in the presence of tin and can also be successfully stripped by using an

aqueous mixture of 4 M HCl + 0.05 M NaClO3. The effect of tin(II) chloride on the

extraction behavior of tetrachloroplatinate(II) [26] in 1.0 to l.5 M hydrochloric acid

into dichloromethane with triphenylphosphine (TPP) were investigated. Tin(II)

chloride increases the rate and efficiency of platinum extraction. Extraction of Pt, Pd,

Ir by macrocyclic polyethers, cis-sin-cis dicyclohexyl-18-crown-6 (DCH18C6 "A")

and dibenzo-18-crown-6 (DB18C6) [27, 28] in organic solvents (1,2-dichloroethane

and chloroform) from 3 to 10 M HCl aqueous solution was studied. Isobutyl methyl

ketone (MIBK) was used for extraction of Pt(IV) from HCl media with complexing

ligand SCN- [29]. Solvent extraction of Pt(II) with 1,3-dimethyl-2-thiourea (DMTU)

[30] from a chloride medium was examined. 1,2-dichloroethane as an extraction

solvent and bromocresol green ion as a counter anion were used. Within 15 min Pt(II)

was extracted into 1,2-dichloroethane quantitatively. The obstructions of Zn(II),

Mn(II), Ag(I), Cu(II), Cd(II) and Pd(II) was eliminated by adding relevant trapping


Page | 106

agents. The pH selective extraction of platinum by using N’N’- dihexyl and phenyl

and N’-hexyl and phenyl derivatives of N-benzoyl thiourea [31] was carried out. The

extraction of platinum(II) and palladium(II) with bis(2,4,4-trimethylpently)

phosphinodithioic acid [32] from chloride solution has been investigated. The effect of

tetraheptylammonium thiocyanate, thiourea and tetraheptylammonium chloride on the

extraction of Pt(II) is studied. Pt(II) was quantitatively extracted by this method. N,N'-

dimethyl-N,N'-diphenyltetradecylmalonamide (DMDPHTDMA) [33] dissolved in

1,2-dichloroethane has been studied as a extraction reagent to mainly perform the

separation of Rh from other PGMs and from some commonly associated elements

contained in concentrated hydrochloric acid media. The developed extraction method

was applied to an automobile catalytic converter leaching solution. n-Butyl

isooctylamide (BiOA) [34] in octane has been studied as a solvent extraction reagent

for extraction of Pt(IV).

N,N'-dipentylethylendiamine-N'-thiocarbaldehyde (L) [35] was used as a

solvent extraction reagent for extraction of Pt(IV) from hydrochloric acid solution at

25°C. Chloroform and toluene were used as solvents. The solvent extraction and

separation of Pt(IV) from HCl solutions were examined by using di-Bu sulfoxide [36]

diluted in kerosene. Separation of Pt(IV) was studied from several common ions like

Ni(II), Fe(II) and Cu(II). The solvent extraction of thiocyanate complexes of PGMs

ions by MIBK [37, 38] in hydrochloric acid medium was studied. Solvent extraction

of Pt(IV) from hydrochloric acid solution was studied by using 2-hydroxy-4-sec-

octanoyl diphenyl ketoxime [39] diluted in kerosene as an extractant. P-50 oxime [40]

diluted in Escaid 100 has been used to extract platinum(II) prepared in situ, from

aqueous chloride solutions. The Pt(II) was subjected to slow atmospheric oxidation

which resulted in low distribution ratio values. The equilibrium distribution of Pt(IV)

between hydrochloric acid and trioctylphosphine oxide [41] in toluene at 303 K was

investigated. The extraction equilibrium constant was found to be Ke = 3.6 × 103. The

solvent extraction of Pt(II) with 12-14,16-membered cyclic tetra thioethers [42] from

chloride medium were investigated. 1,2-dichloroethane as an extraction solvent and

bromocresol green ion as a counter anion were used. However, method required 5 h

for platinum(II) extraction in presence of thiourea. Solvent extraction of Pt(II) by


Page | 107

using N,N'-dipentylethylenediamine-N'-thiocarbaldehyde [43] from 0.1 M

hydrochloric acid solution into toluene and chloroform diluents was examined at 25°C

and a shaking time of 5 min. Extraction of platinum(IV) from HCl media with

solution of two bis(aminophosphonates), such as N,N'-bis[[(dioctyloxyphosphoryl)

methyl]butylamine] and N,N-bis(dipentoxyphosphorylmethyl)-octylamine [44] in

xylene and chloroform was studied. The extraction of Pt(IV) from aqueous HCl

solution with solution of bis(2-ethylhexyl) N-butyl-N-octylaminomethylphosphonate

[45] in xylene and chloroform was investigated.

The extraction of halo complexes of platinum(IV) by dipyrazolonylmethanes

[46] was investigated and developed method was used for the chemical atomic

emission determination. The solvent extraction method was developed for

platinum(IV) by using propiconazole (1) [47] from 3 M hydrochloric acid solutions.

N,N-di(2-ethylhexyl) aminomethylquinoline (DEQ) [48] has been used to develop

selective solvent extraction method for platinum(IV). 1-[2-(2,4-Dichlorophenyl)-4-

propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole [49] was examined for the

extraction of Pt(IV). A novel sulfur-containing extraction reagent, 3,3-diethylthietane

(DETE) [50] was studied for extraction of Pt(IV) from hydrochloric acid solution at

30°C. Extraction of platinum(IV) with dihexyl sulfide (DHS) [51-53] from chloride

medium and the degradation of DHS to dihexyl sulfoxide (DHSO) were examined in

this study. The kinetics of the extraction of Pt(IV) from HCl media with petroleum

sulfoxide (PSO) [54] diluted in kerosene has been investigated. The solvent extraction

reagent nonylthiourea (NTH) [55, 56] dissolved in chloroform was used for extraction

of Pt(IV) from chloride medium at 4.0 M ionic strength has been investigated. It is

found that chloride concentration has a negative effect on the extraction while proton

concentration has no effect on extraction. The Pt ion in deactivated catalyst for the

hydro chlorination reaction of ethyne was extracted by acidic thiourea [57] solution.

The intention of the present work is to reveal some new information about the

use of a 4-heptylaminopyridine as a novel extractant for the extraction and separation

of platinum(IV). The effect of various parameters, like equilibration time, diluents,

concentration of extractant, organic/aqueous (O/A) phase ratio, acidity, loading

capacity, stripping and diversity of ions, has been investigated. The developed method


Page | 108

has been extended for the recovery of platinum from catalysts, Pt–Rh thermocouple

wire, anticancer injections (cytoplatin) and water samples.

The review of literature for comparison of solvent extractive separation of

Pt(IV) is given in Table 1.

Table 1 Summary of methods of solvent extraction of platinum(IV)

System Aqueous

phase

Organic

phase

Special features Ref.

No.

Bis(2,4,4-

trimethylpentyl)

monothiophosphinic

acid (Cyanex 302)

Sulfate,

chloride

and

nitrate

Kerosene

Extraction increases

with increase in

concentration in the

ascending order

sulfate > chloride >

nitrate.

18

Cyanex 923 HCl

Toluene

Strippant 5 M HNO3.

Method applicable

for recovery of metal

ions from synthetic

mixtures.

19

Chloride leach liquors HCl

Kerosene

Recovery of

platinum(IV) 99.9 %

20

Rubeanic acid

(ethanedi- thioamide)

3 M

HCl

TBP

Back extraction with

2 M ammonia

solution.

The best overall

recovery was 75-81

%, it could be

increased to 90 % by

performing the

experiment twice.

21

N,N-diethyl-N’-

benzoylthiourea

(DEBT)

2 M HCl

Toluene

DEBT shows

extraction in the order

of Pd(II)>Pt(II)>

Ru(III)>

Rh(III)>Ir(III)

at ligand/metal ratio >

4.

22

Bis(n-octyl-sulphinyl)

ethane (BOSE)

2-6 M

HCl

Chloroform

or butyl

acetate

Extraction in

presence of

potassium iodide.

Platinum can’t be

separated from

palladium.

23

P-(1,1,3,3-tetramethyl

butyl)phenyl H N,N-

di(2- ethylhexyl)

amino-methyl

0.01- 6 M

HCl

Toluene

High lipophilicity

leads to higher

extraction than that

from N,N-di(2-ethyl

24


Page | 109

phosphonate (HR)

hexyl) amino

methylphosphoric

acid.

Extraction for

precious metals.

Iron(III) interference.

N,N'-dimethyl-N,N'-

diphenyltetradecylmal

on- amide

HCl

-

Effective extraction

in presence of tin(II)

chloride.

Back stripped by

mixture of 0.05 M

NaClO3 + 4 M HCl

25

Triphenylphosphine HCl,

1-1.5 M

1,2-

Dichloro

Ethane

The rate and

efficiency greatly

increased in presence

of tin(II) chloride.

Percentage extraction

depends on time

allowed for extraction

ratio of Pt: Sn(II):TPP

and to less extent on

concentration of

hydrochloric acid.

26

Dibenzo-18-crown-6

(DB18C6) and cis-sin-

cis dicyclohexyl-18-

crown-6 (DCH18C6)

HCl

Dichloroetha

-ne &

Chloroform

Extraction process

applicable for Pd(II),

Ir(III), Rh(III)

28,

27

Methyl iso butyl

ketone

2- 3 M

HCl

MIBK

Extraction in

presence of 5 %

potassium

thiocyanate.

95 % extraction was

achieved.

29

1,3-Dimethyl-2-

thiourea (DMTU)

HCl

1,2-

Dichloroeth

-ane

Phase contact time 15

min.

Interference

eliminated by adding

suitable masking

agents.

30

N’N’- dihexyl and

phenyl and N’-hexyl

and phenyl derivatives

of N-benzoylthiourea

HCl

pH 3

Decane,

chloroform,

solvesso150

& toluene

Temperature and pH

dependent extraction.

Heat at 95o C.

Ni, Fe, Cu interfere.

31

Bis-(2,4,4-trimethyl

pentyl)

phosphinodithioic acid

0.1M

HCl

Heptane

Thiourea was added

to increase therate of

extraction.

Shaking time 1 h.

32

N,N'-dimethyl-N,N'- HCl 1,2- Method was 33


Page | 110

diphenyltetradecyl-

malonamide

(DMDPHTDMA)

Dichloroe-

thane

applicable for

separation of Pt(IV)

from other PGMs.

n-Butyl isooctylamide

(BiOA)

HCl

Octane

Platinum(IV)

extraction

99.5 %.

Water was effective

stripping agent.

34

N,N’-

dipentylethylendiamin

e-N’-

thiocarbaldehyde

HCl

Chloroform

or toluene

Method studied at

25oC

Determination by

NMR and IR

35

Di-butyl sulfoxide HCl

Kerosene

Extraction &

separation was

carried out from

several common

impurities like Cu(II),

Ni(II) and Fe(II).

36

Methyl iso butyl

ketone HCl MIBK

Extraction of

thiocyanate

complexes of PGMs.

37,

38

2-Hydroxy-4-sec-

octanoyl

diphenyl-ketoxime

HCl

Kerosene

Applicable for Pd(II)

and Au(III).

39

P-50 oxime HCl

Escaid 100

Co-extraction of

Pd(II).

40

Trioctylphosphine

oxide

HCl

Toluene

Equilibrium constant

Ke = 3.6 × 103.

41

12-14,16-Membered

cyclic tetra thioethers

HCl

1,2-

Dichloroeth

-ane

Method required 5 h

for platinum(II)

extraction.

Bromocresol green

ion act as a counter

anion.

42

N,N'-

dipentylethylenediami

ne-N'-

thiocarbaldehyde

0.1 M

HCl

Toluene &

Chloroform

Method was studied

at 25°C.

A phase contact time

is 5 min.

43

N,N-

bis(dipentoxyphosphor

ylmethyl)octylamine

and N,N'-

HCl

Xylene &

chloroform

Platinum(IV) and

Palladium(II) can’t

separated from one

another.


Page | 111

bis[[(dioctyloxyphosp

horyl)methyl]butylami

ne]

Platinum(IV)

separated from

Fe(III), Cu(II), Co(II)

and Ni(II).

44

bis(2-ethylhexyl) N-

butyl-N-

octylaminomethyl

phosphonate

HCl

Xylene &

chloroform

High selectivity of

separation from the

contaminants Fe(III),

Ni(II), Co(II) and

Cu(II) ions.

The most efficient at

low acidities.

45

Dipyrazolonylheptane

0.25 M

H2SO4

0.1 M

NH4Cl

Chloroform

Determined by

emission

spectroscopy.

Hg interfered.

46

Propiconazole (1)

HCl

Toluene

Platinum(IV)

extraction depending

upon concentration of

hydrochloric acid.

47

N,N-di(2-ethyl hexyl)

aminomethylquinoline

(DEQ)

HCl

Toluene

Platinum(IV)

extraction depending

upon concentration of

hydrochloric acid.

48

1-[2-(2,4-

dichlorophenyl)-4-

propyl-1,3-dioxolan-2-

ylmethyl]-1H-1,2,4-

triazole

HCl

Toluene

Extraction follows the

anion-exchange

mechanism.

49

3,3-diethylthiethane

(DETE)

HCl

Toluene

Extraction was

achieved at 30oC.

Platinum(IV) was

extracted as a

solvated complex of

type PtCl4.4DETE.

50

Dihexyl sulphide

(DHS)

Chloride - Extraction of small

amounts of

platinum(IV) causes

oxidation of DHS to

DHSO as well as the

reduction of

platinum(IV) to

platinum (II).

51-

53

Insoluble substance

was decreased by the

addition of modifier

like alcohol.


Page | 112

Extraction of

platinum(IV)

increased by increase

of phase contact time

and decrease of

palladium(II)

concentration.

Petroleum sulfoxide

(PSO)

HCl

Kerosene

Effect of H+ and Cl-

ions, temperature,

stripping is studied.

54

Nonylthiourea (NTH)

HCl Chloroform

Heating is required. 55,

56

Thiourea HCl

Ethyne

98 % extraction was

achieved.

57

4.3 Experimental

4.3.1 Apparatus

UV/VIS Spectrophotometer model-Optizen α (mecasys Co., Ltd/made in

Korea) with 1cm quartz cell has used for absorbance measurements and pH

measurements are carried out with an Elico Digital pH meter Model LI-120 with a

combined glass electrode.

4.3.2 Reagents

4.3.2.1 Standard platinum(IV) solution

A standard solution of platinum(IV) was prepared by dissolving 1 g (1 X 10-3

kg) of hydrogen hexachloroplatinate(IV) hydrate, H2PtCl6 .H2O (Johnson and

Matthey, UK), in 1 M hydrochloric acid and was standardized gravimetrically [58]. A

working solution (200 µg mL-1) was made using the appropriate dilution.

4.3.2.2 4-Heptylaminopyridine solution (0.06 M)


sodium amide was added at 0 oC and stirring was continued for 30 min. The

temperature of the reaction mixture increased to room temperature and 1-

bromoheptane was added slowly. The reaction mixture was stirred at ambient

temperature for 1 h. The reaction mixture was poured into water containing NH4Cl

and extracted with chloroform (150 mL). The chloroform extract was dried (Na2SO4)

and evaporated using a rotary evaporator to yield a residue which was crystallized to

afford the corresponding 4-heptylaminopyridine in 75–85% overall yield [59] and it's


Page | 113

solutions were prepared in xylene. Other standard solutions of diverse ions were

prepared by dissolving weighed quantities of their salts in water or dilute HCl [60].

Different synthetic mixtures containing platinum(IV) were prepared by combining

with commonly associated metal ions in definite compositions [61]. All of the other

chemicals and solvents were of AR grade and double distilled water was used

throughout the experiments.

4.3.2.3 Stannous chloride solution (25% w/v)

Stannous chloride (25 g) was dissolved in 25 mL of conc. hydrochloric acid

and diluted with water to 100 mL.

4.3.3 Extraction procedure










hydrochloric acid.

4.3.4 Estimation procedure for platinum(IV)

The resulting aqueous phase was mixed with 5 mL of concentrated

hydrochloric acid and 10 mL of 25% stannous chloride. The solution was diluted to

the mark with water in a 50 mL volumetric flask. The absorbance of the resultant

solution was measured at 403 nm [61]. The concentration of platinum(IV) was

calculated in terms of percentage extraction (%E).

4.4 Results and discussion

4.4.1Extraction of platinum(IV) as a function of pH

Extraction of platinum(IV) was performed between pH 0.10 and 6.0 in a fixed

concentration of 0.007 M of ascorbic acid using a 0.06 M solution of 4-

heptylaminopyridine in xylene. The extraction was found to be quantitative within a


Page | 114

pH range of 0.5 to 2.0 (Fig. 1). With an increase in the pH to above 2.0 the extraction

kept decreasing. Hence, the extraction of platinum(IV) was carried out at pH 1.5 for

all of the extraction experiments (Table 2). The decrease in extraction with the

increase in pH value was due to the hydrolysis of the ion–pair complex.

4.4.2 Extraction as a function of weak organic acid concentration

The extraction behavior of platinum(IV) from ascorbic acid, sodium salicylate,

sodium malonate and sodium succinate at pH 1.5 using 0.06 M 4-heptylaminopyridine

in xylene was studied (Table 3). The extraction initiated in 0.001 M ascorbic acid and

became quantitative in the concentration range of 0.005 to 0.01 M. With the

increasing concentration of ascorbic acid, there was a decrease in the extraction of

platinum(IV). This may be due to formation of stable 4-heptylaminopyridine–

ascorbate species. Therefore, 0.007 M ascorbic acid was used throughout this work.

There was incomplete extraction of platinum(IV) from malonate, salicylate and

succinate media (Fig. 2).

4.4.3 Effect of extractant concentration

The effect of extractant concentration in the range of 0.01 to 0.1 M of 4-

heptylaminopyridine in xylene was studied for the extraction of 200 µg of

platinum(IV) from 0.007 M ascorbic acid (Table 4). It was found that 10 mL of 0.055

M extractant was sufficient for the quantitative extraction of the 200 µg of

platinum(IV) from 0.007 M ascorbic acid. However, in the recommended procedure

10 mL of 0.06 M 4-heptylaminopyridine in xylene was used to ensure the complete

extraction of the metal ion. There was no adverse effects of using an excess of 4-

heptylaminopyridine (Fig. 3).

4.4.4 Effect of diluents

The extraction of the 200 µg of platinum(IV) from 0.007 M ascorbic acid

media using 0.06 M 4-heptylaminopyridine in various aliphatic and aromatic diluents,

like n-hexane, benzonitrile, kerosene, cyclohexane, benzyl alcohol, toluene, xylene,

dichloroethane, chloroform, and carbon tetrachloride was tested (Table 5). The

extraction of platinum(IV) was quantified with inert diluents, such as xylene and

toluene, because the ion–pair complex has a high distribution ratio value in these

solvents. Whereas carbon tetrachloride (47%), kerosene (52.4%) and chloroform


Page | 115

(89.7%) were found to be poor solvents (Fig. 4), while there was no extraction in n-

hexane, benzonitrile, benzyl alcohol, dichloroethane and cyclohexane. No correlation

between dielectric constant and percentage extraction was observed. In the present

study, xylene was used as the diluent as it is cheap, there is no emulsion formation and

the phase separation took place rapidly.

4.4.5 Effect of equilibration time

The extraction behavior of platinum(IV) from ascorbic acid media using 0.06

M 4- heptylaminopyridine in xylene has been measured at different equilibration

times of 6 s to 20 min (Table 6). It has been observed that, under the optimized

experimental conditions, a minimum 25 second time interval is required for attaining

equilibrium in order to extract platinum(IV) quantitatively. In the recommended

procedure, a 2 min equilibration time was recommended for ensuring the complete

extraction of platinum(IV). However, a prolonged shaking period was found to have

an adverse effect on the extraction and should be avoided (Fig. 5). This may be due to

the dissociation of the ion–pair complex.

4.4.6 Stripping of platinum(IV) from the loaded organic phase

Back stripping is the reverse process of extraction. Therefore, stripping of

platinum(IV) from the loaded organic phase was carried out using NH3, ammonia

buffer (pH 10), H2O, HCl, HNO3, H2SO4, NaCl, KOH and NaOH (Table 7). The

stripping of platinum(IV) was quantified with water. The stripping was found to be

incomplete using NaCl (12.7%), NH3 (20.6%), ammonia buffer (pH 10) (27%), NaOH

(35.8%), KOH (42.3%), HCl (52.3%) and HNO3 (55.9%). In the recommended

procedure, two 10 mL portions of water were used for the complete stripping of the

loaded organic phase.

4.4.7 Effect of aqueous to organic volume ratio

The results of using different volume ratios of aqueous to organic phases have

been studied. The results indicate that the preferred aqueous/organic (A/O) phase ratio

in this study was 2.5 : 1. This is evident from the sharp increase in the separation

efficiency, as well as the distribution ratio of platinum(IV), when the phase ratio

(A/O) changed from 10 : 1 to 5 : 1. This may simply be due to the unavailability of

reagent for metal extraction and so a crowding effect occurs at a low phase ratio.


Page | 116

However, in the recommended procedure, the phase ratio was maintained as 2.5 : 1

(Table 8).

4.4.8 Metal loading capacity of extractant

The loading capacity of 0.06 M 4-heptylaminopyridine was determined by

using 10 mL of the organic phase for 2 min repeatedly with the 25 mL of aqueous

phase containing varied concentrations of platinum(IV) (Table 9). The maximum

loading capacity of 10 mL of a 0.06 M solution of 4-heptylaminopyridine in xylene

was found to be 2000 µg of platinum(IV) (Fig. 6).

4.4.9 Mechanism for the extraction of platinum(IV)

Attempts were made to ascertain the nature of the extracted species using log

D–log C plots. The graphs of log D[Pt(IV)] against log C[4-HAP] at a fixed ascorbic acid

concentration (0.007 M) were found to be linear, having slopes of 0.78 and 0.77 at pH

2 and 2.25, respectively (Fig. 7). Also, plots of log D[Pt(IV)] against log C[ascorbic acid] at

fixed 4-heptylaminopyridine concentration (0.06 M) were linear and the slope values

were found to be 2.78 and 2.87 at pH 2 and 2.25, respectively (Fig. 8). The probable

composition of the extracted species was calculated to be 1 : 3 : 1 (metal : acid :

extractant). In the extraction of platinum(IV) with ascorbate medium, the first

platinum(IV) was reduced to platinum(II) [63] then it was converted into a

platinum(II) ascorbate species as an anionic complex and interacted with RR’NH2+.

Hence, the probable extracted species in xylene are [RR’NH2+.Pt(C6H7O6)3

-]org

species.

The probable mechanism of extraction is:

RR'NH(org) + H+ascorbate(aq)- [RR'NH2

+ascorbate-](org) (1)

H2PtIVCl6Ascorbic acid

Reducing agentPtIICl4

2- + 2 HCl (2)

Pt2+ + 3 ascorbate- [Pt(ascorbate)3](aq)-

(3)

[Pt(ascorbate)3](aq)-

[RR'NH2+ascorbate-](org)

[RR'NH2+ Pt(ascorbate)3

-](org) + ascorbate(aq)-(4)+

Probable Stripping mechanism:


Page | 117

[RR'NH2+ Pt(ascorbate)3

-](org) + H2O RR'NH + H3O+ + Pt(ascorbate)3

- (5)

4.4.10 Effect of various foreign ions on percentage extraction

The effects of various diverse ions on the extraction of platinum(IV) using 4-

heptylaminopyridine in xylene were tested. The tolerance limit of individual diverse

ions was determined with an error of less than ± 2%. It was observed that the method

is free from interference from a large number of cations and anions (Table 10). The

only species that showed interference in the procedure were Pd(II), Rh(III), iodide,

thiocyanate, thiourea and thiosulphate. However, the interference due to co-extraction

of Pd(II) and Rh(III) was eliminated by masking with tartrate. However, thiocyanate,

thiosulphate and thiourea make very strong complexes with platinum(IV). This is due

to soft acid and soft base combination while iodide ions form strong anionic species

with platinum(IV).

4.5 Applications

4.5.1 Separation and determination of platinum(IV) from binary mixtures

The separation of Pt(IV) from some commonly associated metal ions like

Ru(III), Os(VIII), Ir(III), Rh(III), Au(III), Fe(III), Co(II), Ni(II), Hg(II), Cd(II), Zn(II),

Pd(II), Bi(III), Te(IV), and Ag(I) using 4-heptylaminopyridine was achieved by taking

advantage of the difference in the extraction conditions of the metals, such as the pH

of the aqueous phase, reagent concentration and use of masking agent (Table 11). All

of the added metal ions remained quantitatively in the aqueous phase from which they

were determined spectrophotometrically using standard methods [60, 61]. Rh(III) and

Pd(II) interfered with the procedure due to their co-extraction with Pt(IV). Rh(III) and

Pd(II) were separated from Pt(IV) by masking them with 10 mg of tartrate. The

masked metal ions from the aqueous phase were de-masked with perchloric acid and

determined spectrophotometrically using the standard method [61].

4.5.2 Separation of platinum(IV) from ternary synthetic mixtures

Platinum(IV) is one of the platinum group metals (PGMs), and therefore, it was

separated from Ru(III) and Ag(I); and Rh(III) and Pd(II). The Rh(III) and Pd(II) were

masked by tartrate as a masking agent. Other platinum group metals were not


Page | 118

extracted with the optimum extraction conditions of platinum(IV). Platinum(IV) was

also isolated from Os(VIII) and Te(IV); Ir(III) and Bi(III); Au(III) and Zn(II); Fe(III)

and Cd(II); Co(II) and Hg(II); Ni(II) and Ru(III); Hg(II) and Os(VIII); Cd(II) and

Ir(III); Zn(II) and Cd(II); Pd(II) and Fe(III); and Ag(I) and Bi(III). The results are

found to be quantitative (Table 12).

4.5.3 Determination of platinum(IV) in catalyst samples

A catalyst (0.1 g) was dissolved in 5 mL of aqua regia. The solution was

evaporated to moist dryness. Two 3 mL portions of hydrochloric acid were added and

evaporated until all of the nitric acid was removed. The residue was extracted in 1 M

hydrochloric acid. The solution was filtered and the filtrate was diluted to 100 mL. An

aliquot of this diluted solution was analyzed for its platinum(IV) content using the

proposed method. It was found that there is a good agreement with the certified value

(Table 13).

4.5.4 Analysis of anticancer injections (cytoplatin)

The method permits the separation and determination of platinum(IV) from

anticancer injections (cytoplatin). A known volume (10 mL) of cisplatin solution was

digested in perchloric acid/nitric acid (10 : 1) and evaporated to dryness until the

organic matter was removed. The obtained residue was dissolved in concentrated

hydrochloric acid and diluted with water to 10 mL in a standard volumetric flask. An

aliquot of the sample solution was taken and the amount of platinum(IV) was

determined using the recommended procedure (Table 14).

4.5.5 Analysis of Pt–Rh thermocouple wires for platinum content

The proposed procedure was used for the estimation of the amount of

platinum(IV) in a Pt–Rh thermocouple wire (Table 14). A known weight (0.100 g) of

thermocouple wire was preliminarily fused with zinc powder and the melt was cooled

and dissolved in hydrochloric acid. The black powder remaining was treated with 5

mL of aqua regia. After the reaction was over, the whole solution was heated with two

5 mL portions of concentrated hydrochloric acid until the complete removal of the

oxides of nitrogen and diluted with water to 10 mL in a standard volumetric flask. An

aliquot of the sample solution was taken and the amount of platinum(IV) was

determined using the recommended procedure.


Page | 119

4.5.6 Determination of platinum(IV) in water samples

In order to investigate the accuracy and applicability of the method, it was used

for the determination of platinum(IV) in water samples collected from different

sources. The water samples that were collected were filtered through Whatman filter

paper no. 40 to remove suspended matter, impurities etc., and then boiled for 5 min to

remove chlorine and dissolved gases. Then, the water samples were spiked with 200

µg of platinum(IV) and the developed method was applied for the determination of

platinum(IV) in the spiked water samples. The results were in good agreement with

the amount of platinum(IV) added (Table 15).

4.6 Conclusions

4-Heptylaminopyridine has been proven to be a sensitive, selective extractant

for the separation of platinum(IV) from commonly associated metal ions. The

developed method is simple, reproducible and requires less time for the separation of

platinum(IV). The important features of the proposed methods are,

(i) A low concentration of extractant is required for the quantitative extraction of

platinum(IV).

(ii) 4-Heptylaminopyridine forms an ion–pair complex with platinum(IV) in ascorbic

acid medium.

(iii) Extraction of platinum(IV) has been carried out without the addition of any

synergent or modifier at room temperature.

(iv) Ecofriendly strippant (water) is used for the stripping of platinum(IV); its use in

this method follows one of the principles of green chemistry.

(v) The developed method is free from interference from a large number of diverse

ions which are commonly associated with platinum(IV). The selectivity was also

enhanced using suitable masking agents.

(vi) The developed method is reproducible, simple and can be used for the extraction

of platinum(IV) from binary and ternary metal ion mixtures.

(vii) The developed method has been successfully used for the extraction of

platinum(IV) from real samples such as catalysts, Pt–Rh thermocouple wires,

anticancer injections and water samples.


Page | 120

Table 2 Extraction of platinum(IV) as a function of pH

Platinum(IV) = 200 μg Aq.: Org. = 2.5: 1

Ascorbic acid = 0.007 M Org. = 0.06 M 4-HAP in xylene (10 mL)

Strippant = Water (2×10 mL)

pH Percentage extraction, (% E) Distribution ratio, (D)

0.10 35.0 1.34

0.25 65.0 4.64

0.50 100 ∞

0.75 100 ∞

1.0 100 ∞

1.25 100 ∞

1.50* 100 ∞

1.75 100 ∞

2.0 100 ∞

2.25 60.4 3.81

2.50 25.2 0.84

3.0 16.1 0.47

4.0 10.2 0.28

5.0 4.98 0.13

6.0 2.05 0.052



Page | 121

Table 3 Extraction as a function of weak organic acid concentration

Platinum(IV) = 200 μg Aq.: Org. = 2.5: 1

Org. = 0.06 M 4-HAP in xylene (10 mL) pH = 1.5


Acid conc. (M)

Ascorbic acid Sodium

salicylate

Sodium

malonate

Sodium

succinate

% E D % E D % E D % E D

0.001 40.4 1.69 34.3 1.30 32.2 1.18 29.3 1.03

0.002 55.1 3.06 43.4 1.91 39.2 1.61 35.1 1.35

0.004 85.0 14.1 63.0 4.25 51.3 2.63 43.4 1.91

0.006 100 ∞ 70.6 6.00 54.2 2.95 44.2 1.98

0.008 100 ∞ 59.5 3.67 54.2 2.95 45.4 2.07

0.01 100 ∞ 53.6 2.88 54.2 2.95 44.5 2.00

0.02 69.2 5.61 48.9 2.39 54.2 2.95 43.4 1.91

0.03 46.3 2.15 46.3 2.15 53.3 2.85 42.5 1.84

0.04 30.2 1.08 43.9 1.95 51.3 2.63 40.4 1.69

0.05 19.0 0.58 40.5 1.70 49.5 2.45 38.4 1.55

% E = Percentage Extraction D = Distribution Ratio

0.007 M Ascorbic acid recommended for general extraction procedure


Page | 122

Table 4 Effect of extractant concentration

Pt(IV) = 200 µg pH = 1.5

Ascorbic acid = 0.007 M Aq.: Org. = 2.5:1


4-HAP, (M) Percentage extraction, (% E) Distribution ratio, (D)

0.010 26.3 0.89

0.015 32.2 1.18

0.020 39.5 1.63

0.025 46.3 2.15

0.030 53.9 2.92

0.035 61.2 3.94

0.040 70.3 5.91

0.045 80.3 10.1

0.050 92.3 29.9

0.055 100 ∞

0.060* 100 ∞

0.065 100 ∞

0.070 100 ∞

0.080 100 ∞

0.090 100 ∞

0.10 100 ∞



Page | 123

Table 5 Effect of diluents

Pt(IV) = 200 µg pH = 1.5


Strippant = Water (2×10 mL) Org. = 0.06 M 4-HAP (10 mL)

Solvent Dielectric

constant

Percentage extraction,

(% E)

Distribution

ratio, (D)

Xylene* 2.30 100 ∞

Toluene 2.38 100 ∞

Chloroform 4.81 93.5 35.9

Dichloromethane 8.93 35.1 1.35

Dichloroethane 1.25 40.7 1.71

Methyl isobutyl

ketone (MIBK)

13.11 63.9 4.42

Cyclohexane 2.02 75.0 7.5

Amyl alcohol 13.90 45.4 2.07

Kerosene 1.8 52.4 2.75



Page | 124

Table 6 Effect of equilibration time

Platinum(IV) = 200 µg pH = 1.5


Strippant = Water (2×10 mL) Org. = 0.06 M 4-HAP in xylene (10 mL)

Time in min

Percentage extraction, (%E )

Distribution ratio, ( D )

0.10 55.7 3.14

0.25 100 ∞

0.50 100 ∞

1.0 100 ∞

2.0* 100 ∞

3.0 100 ∞

4.0 100 ∞

5.0 100 ∞

6.0 100 ∞

7.0 100 ∞

8.0 100 ∞

9.0 100 ∞

10.0 100 ∞

15.0 70.3 5.91

20.0 39.2 1.61



Page | 125

Table 7 Stripping of Pt(IV) from the loaded organic phase

Platinum(IV) = 200 µg pH = 1.5


Strippant = Water (2×10 mL) Org. = 0.06 M 4-HAP in xylene (10 mL)

Equilibrium time = 2 min

Stripping agents Percentage Extraction, (%E) Distribution ratio, (D)

Ammonia (1-10M) 20.6 0.64

Ammonia buffer (pH10) 27.0 0.92

HCl (1-10M) 52.3 2.74

Water* 100 ∞

HNO3 (1-10M) 55.9 3.16

NaCl (0.1-1.3M) 12.7 0.36

KOH (0.1-1.5M) 42.3 1.83

NaOH (0.1-1.5M) 35.8 1.39



Page | 126

Table 8 Influence of aqueous to organic volume ratio

Pt(IV) = 200 µg pH = 1.5

Ascorbic acid = 0.007 M Strippant = Water (2×10 mL)

Equilibrium time = 2 min Org. = 0.06 M 4-HAP in xylene (10 mL)

Aqueous to organic

volume ratio

Percentage extraction, (% E)


10:10 100 ∞

20:10 100 ∞

25:10* 100 ∞

30:10 100 ∞

35:10 100 ∞

40:10 100 ∞

50:10 100 ∞

75:10 72.4 6.55

100:10 32.2 1.18



Page | 127

Table 9 Metal loading capacity of extractant

pH = 1.5 Aq.: Org. = 2.5:1



Platinum(IV), (μg)

Percentage extraction, (% E)


100 100 ∞

200* 100 ∞

400 100 ∞

800 100 ∞

1000 100 ∞

1500 100 ∞

2000 100 ∞

3000 96.4 66.9

4000 88.5 19.2

5000 79.7 9.81



Page | 128

Table 10 Effect of various foreign ions on percentage extraction

Platinum(IV) = 200 µg pH = 1.5 Aq.: Org. = 2.5:1



Amount tolerated (mg) Diverse ion added

25 Ca(II), Zn(II), malonate, fluoride

15 U(VI), Mo(VI), Tl(III), tartrate, citrate, oxalate, acetate,

bromide

10 Ti(IV), V(V), Ni(II), Cd(II), Pb(II), Te(IV), Mg(II), Be(II),

EDTA, nitrate

5 Hg(II), Cr(III), Cr(VI), Fe(II), Fe(III), Bi(III), Se(IV),

succinate, salicylate, chloride

3 Rh(III)a,Os(VIII), Au(III)

2 Re(VII), Pd(II)a, Ru(III), Ag(I), Ir(III)

0 Iodide, thiocyanate, thiourea, thiosulphate

aMasked with 10 mg tartrate


Page | 129

Table 11 Separation and determination of Pt(IV) from binary mixtures

Metal ion Amount

taken(µg)

Average

recovery(%)a

Chromogenic ligand Reference

Pt(IV)

Ru(III)

200

200

99.4

97.9

Thiourea

62

Pt(IV)

Fe(III)

200

60

99.4

99.1

Thiocyanate

61

Pt(IV)

Ni(II)

200

40

99.1

98.5

DMG

61

Pt(IV)

Co(II)

200

300

99.3

98.1

Thiocyanate

61

Pt(IV)

Pd(II)b

200

80

99.1

98.9

Dithizone

61

Pt(IV)

Os(VIII)

200

300

99.1

98.8

Thiourea

62

Pt(IV)

Ir(III)

200

40

98.8

98.2

Hydro bromic acid

61

Pt(IV)

Au(III)

200

200

98.9

98.8

Stannous chloride

62

Pt(IV)

Rh(III)b

200

200

98.9

99.3

Potassium iodide

61

Pt(IV)

Hg(II)

200

100

99.0

99.2

PAN

60

Pt(IV)

Zn(II)

200

60

99.1

99.4

PAR

60

Pt(IV)

Cd(II)

200

10

99.1

98.5

PAR

60

Pt(IV)

Bi(III)

200

300

98.5

97.8

Potassium iodide

61

Pt(IV)

Te(IV)

200

120

98.8

98.5

Bismuthiol II

61

Pt(IV)

Ag(I)

200

120

98.8

98.6

Rhodanine

61


bMasked with 10 mg tartrate


Page | 130

Table 12 Separation of platinum(IV) from ternary synthetic mixtures

Composition (µg) Average recoverya (%) RSD (%)

Pt(IV), 200; Ru(III), 200; Ag(I), 120 99.6 0.45

Pt(IV), 200; Rh(III)b, 200; Pd(II)b, 80 99.3 0.67

Pt(IV), 200; Os(VIII), 300; Te(IV), 120 99.9 0.1

Pt(IV), 200; Ir(III), 40; Bi(III), 300 99.7 0.18

Pt(IV), 200; Au(III), 200; Zn(II), 60 99.8 0.13

Pt(IV), 200; Fe(III), 60; Cd(II), 10 99.9 0.15

Pt(IV), 200; Co(II), 300; Hg(II), 100 99.8 0.09

Pt(IV), 200; Ni(II), 40; Ru(III), 200 99.9 0.17

Pt(IV), 200; Hg(II), 100; Os(VIII), 300 99.8 0.09

Pt(IV), 200; Cd(II), 10; Ir(III), 40 99.9 0.09

Pt(IV), 200; Zn(II), 60; Cd(II), 10 99.9 0.17


bMasked with 10 mg of tartrate


Page | 131

Table 13 Determination of platinum(IV) in catalystsa

Catalyst Pt(IV)

taken

(µg)

Pt(IV) found using the

proposed methodb (µg)

Average,

% recovery

RSD

(%)

Pt-Pdc-Rhc

monolith on cordierite1

200

199.6

99.8

0.1

Pt–Rhc

monolith on cordierite2

200

199.4

99.7

0.18

Pt catalyst on

alumina3

200

199.2

99.6

0.21

Pt–Pdc–Rhc

catalyst on alumina4

200

199.6

99.8

0.1

Pt–Pdc catalyst on

alumina5

200

199.4

99.7

0.13

Pt–Rhc

catalyst on alumina6

200

199.4

99.7

0.15

aComposition of synthetic mixtures in percentage:

1. Pt, 0.03–0.20; Pd, 0.03–0.15; Rh, 0.005–0.05

2. Pt, 0.03–0.25; Rh, 0.005–0.03

3. Pt, 0.3–0.8

4. Pt, 0.03–0.20; Pd, 0.03–0.150; Rh, 0.005–0.05

5. Pt, 0.03–0.15; Pd, 0.02–0.12

6. Pt, 0.03–0.25; Rh, 0.005–0.03

bAverage of five determinations

cMasked with tartrate


Page | 132

Table 14 Analysis of platinum(IV) in the anticancer injection and thermocouple wire

Sample Amount taken Amount of Pt(IV)

founda

RSD, (%)

Cytoplatin

(anticancer injection)

200 µg/mL 198.2 µg/mL 0.35

Platinum–rhodiumb

thermocouple wire

(Pt, 87%; Rh, 13%)

200 µg/mL 197.4 µg/mL 0.25


bMasked with 10 mg tartrate

Table 15 Determination of platinum(IV) in water samples

Sample platinum(IV)

spiked (µg)

platinum(IV)

found (µg)

Average

recoverya

(%)

RSD

(%)

Distilled waterb 200 199.86 99.9 0.04

Tap waterb 200 199.80 99.9 0.06

Waste waterb 200 199.66 99.8 0.29

River waterc 200 199.40 99.7 0.33


bDepartment of Chemistry, R. R. College, Jath Dist-Sangli

cPanchganga River, Kolhapur


Page | 133

Fig. 1 Extraction of platinum(IV) as a function of pH

Conditions:

Platinum(IV) = 200 µg, ascorbic acid = 0.007 M, 4-HAP = 0.06 M in xylene,

equilibration time = 2.0 min., strippant = water (2×10 mL),

aq. : org. volume ratio = 2.5 : 1,


Page | 134

Fig. 2 Extraction as a function of weak organic acid concentration

Conditions:

Platinum(IV) = 200 µg, pH = 1.5, 4-HAP = 0.06 M in xylene, equilibration time = 2.0 min.,

strippant = water (2×10 mL), aq. : org. volume ratio = 2.5 : 1


Page | 135

Fig. 3 Effect of extractant concentration

Conditions:

Platinum(IV) = 200 µg, pH = 1.5, ascorbic acid = 0.007 M, equilibration time = 2.0 min.,

aqueous: organic volume ratio = 2.5 : 1, strippant = water (2×10 mL)


Page | 136

Fig. 4 Effect of diluents

Conditions:

Platinum(IV) = 200 µg, pH = 1.5, ascorbic acid = 0.007 M, 4-HAP = 0.06 M in variable

solvent, equilibration time = 2.0 min., aq. : org. volume ratio = 2.5 : 1, strippant = water

(2×10 mL)


Page | 137

Fig. 5 Effect of equilibration time

Conditions:

Platinum(IV) = 200 µg, pH = 1.5, ascorbic acid = 0.007 M, 4-HAP = 0.06 M in xylene,



Page | 138

Fig. 6 Metal loading capacity of extractant

Conditions:

pH = 1.5, ascorbic acid = 0.007 M, 4-HAP = 0.06 M in xylene, equilibration time = 2 min.,



Page | 139

Fig. 7 Log-log plot of distribution ratio Log D[Pt(IV)] versus Log C[4-HAP] at fixed ascorbic

acid concentration

Conditions:

Platinum(IV) = 200 µg, ascorbic acid = 0.007 M, pH = 2 and 2.25, equilibration time = 2.0

min., aqueous : organic volume ratio = 2.5 : 1, strippant = water (2×10 mL)


Page | 140

Fig. 8 Log-log plot of distribution ratio Log D[Pt(IV)] versus Log C[ascorbic acid] at fixed 4-

heptylaminopyridine concentration

Conditions:

Platinum(IV) = 200 µg, pH = 2 and 2.25, 4-HAP = 0.06 M in xylene, equilibration time = 2.0

min., strippant = water (2×10 mL), aq. : org. volume ratio = 2.5 : 1


Page | 141

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Publications


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List of Published Papers in Journals

Sr.

No.

Title Journal Impact

Factor

01



the selective separation of palladium(II)

from synthetic mixtures, catalysts and

water samples

Desalination and Water

Treatment

(Taylor & Francies)

1.272

02



the selective separation of platinum(IV)

from catalysts, anticancer injections

and water samples

Analytical

Methods(RSC)

1.915


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ACKNOWLEDGEMENT

The author is thankful to the University Grants Commission, Western

Regional Office, Pune, for sanctioning and funding this Minor Research

Project.

It gives me great pleasure to express my sincere sense of gratitude to

Trustees of Shri Swami Vivekananda Shikshan Sanstha, Kolhapur, Principal

Dr. S. Y. Hongekar and I/C Principal Dr. V. S. Dhekale for all their support,

kind co-operation and continuous encouragement.

I wish to express my warm and sincere thanks to Prof. M. A. Anuse,

Professor in Inorganic Chemistry, Shivaji University, Kolhapur for valuable

guidance and co-operation. The author is thankful to Shri. K. K. Rangar Head

of Chemistry Department and colleagues Dr. S. R. Kulal, Mr. D. A. Kumbhar,

Mr. G. D. Salunke, Mr. B. T. Khogare, teaching and administrative staff of the

college for their full co-operation and help in completing this research work.

Dr. S. R. Kokare Dr. B. N. Kokare

university grants commission research project: by dr. b. n. kokare, raje ramrao mahavidyalaya, jath,...

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