CHAPTER VII

Application of extractants for the extraction

of Ruthenium(III)

7.1 Introduction:

Ruthenium is a scarce element that is found in about 10–8 % of the earth's

crust. It is present in much larger amounts in chondrite and, especially, in iron

meteorites ((1-6)×10–4%). It usually occurs in association with other platinum group

metals [1].

As one of the most effective hardeners in high-density alloys, ruthenium is

widely used in the electronic industry. Alloyed with other platinum metals, it serves

to make electrical contacts for heavy wear resistance. The addition of 0.1% of

Ruthenium to Titanium improves its’ corrosion resistance by a factor of 100. It is an

important catalyst in the chemical industry. Some Ruthenium compounds are

undergoing clinical trials against cancer [2].

Recently, platinum group metals, especially ruthenium and its

chlorocomplexes, have been much used in the catalytic oxidation of some organic

compounds. Ruthenium and its alloys also have a widespread application in

jewellery [1]. In radiochemistry, the interest lies in the separation of rhodium from

ruthenium since rhodium is a daughter of ruthenium by beta decay [3]. It is a

versatile catalyst, used in the selective reduction of carbonyl groups in organic

compounds by hydrogen and the removal of hydrogen sulfide from oil refinery and

other industrial processes.

However, the scarcity of this metal has led to mining from low-grade ores

where these metals are present in trace levels. Since platinum metal materials retain

a large proportion of their initial value, resulting in the occurrence of many diverse

scrap materials that are sources of recoverable platinum group metals [4]. Therefore,

the recovery and recycling of these metals have become important. When ruthenium

is present in various matrices in extremely low concentrations, direct determination

is not successful without previous preconcentration and separation. Separation

procedures like volatilization, coprecipitation, solvent extraction, sorption and

chromatography, can be used to isolate and preconcentrate ruthenium from

multicomponent samples containing noble and base metals [5].

167

A conventional method for the separation of ruthenium from the platinum

metals is based on the distillation of volatile ruthenium tetroxide [6,7]. Different

oxidants (HClO4+H2SO4, NaBiO3, K2Cr2O7 and KMnO4) for ruthenium have been

used. This, however, is not an appropriate method for producing ruthenium on an

industrial scale because it requires complicated manipulation and because of the

explosive property of tetroxide at temperatures above 180°C. Therefore, solvent

extraction is preferred to distillation [2]. For metal preconcentration, the tetroxide

can be extracted into carbon tetrachloride [8-10], chloroform,[8] or mephasine [11].

Various complexing agents (e.g., di (2-ethylhexyl) - phosphonic acid [12]

carbamates [9] dithizone [9] and thiourea derivatives [9]) can be used in the

separation procedures to convert ruthenium into stable extractable species. The

chlorocomplexes of ruthenium are extractable by means of various

organophosphorus compounds [13] and high-molecular-weight amines [13,14].

Amine, dissolved in an organic solvent, is transformed into organic cation (RxNH+)

by reacting with the acid present in aqueous solution. The cation reacts with an

anionic complex of the analyte in solution by forming an ion-pair, dissolved in the

organic solvent used as diluent.

Ruthenium can be separated from platinum metals after its conversion into a

thiocyanate complex [15–19]. A high distribution coefficient is achieved when

polyurethane foam is applied in ruthenium extraction from thiocyanate media [18].

Extraction of ruthenium from thiocyanate media into Triton X-100 phase in the

presence of Zephiramine has been investigated [19].

Solvent-extraction processes are well established and efficient techniques for

the separation of ruthenium from platinum and palladium [14,20], rhodium [16,20],

osmium, and iridium [20,21].

UV-VIS spectrophotometry is widely applied for the determination of

microgram amounts of ruthenium. Extraction is the first step to be taken before

spectrophotometric determination of ruthenium [14, 22-33]. Various

spectrophotometric methods have been proposed for ruthenium determination, but

have low sensitivity which makes them unsuitable for the determination of trace

168

level ruthenium [34-36]. Compared with other organic reagents, when the

heterocyclic azo derivatives [37-40] and sulfur containing compounds [41,42] are

used as extractants the efficiency of extraction increased. On the other hand, it is well

known that the sensitivity and the selectivity can also be increased by ion-pair

solvent extraction [43-45] and by using derivative spectrophotometry [46-51], but in

derivative spectrophotometry prolonged heating is required.

Ruthenium, was extracted from hydrochloric acid media using cynex 921 [52]

and method was applied for recoveries of metal ions from catalyst samples.

Extraction of ruthenium in column chromatography has been studied in chloride

media using alamine 336 and TBP [53] in kerosene and separation of nonvolatile

platinum metals was achieved. Iridium, ruthenium and rhodium were extracted

from chloride solution using different commercially available extractants. The

mixture of alamine 336, LIX-54 and aliquot 336 [55] LIX-54 were effective for the

extraction of ruthenium(III). Platinum, palladium, ruthenium, rhodium and iridium

were extracted with N,N-diethyl-N-benzoylthiourea [56] in hydrochloric acid media.

Solvent extraction of ruthenium(IV) has been carried out using N-octylaniline [57]

from hydrochloric acid medium and stripped with 2.0% sodium chloride solution,

however, it suffers due to interferences from iron(II), lead(II), cadmium(II),

manganese(II), bismuth(III), cerium(IV), and tellurium(IV). 4-Octylaniline has been

reported to be group extracted for noble metals [58,59]. Noble metals were extractant

using n-octylaniline but effectiveness of extraction depends on the method of

preparation [60].

The various reported methods differ considerably in sensitivity, tolerance to

other ions, rate of reaction, and useful concentration range. A large number of

organic reagents, such as 8-hydroxyquinoline [61], oximes [62-68],

thiosemicarbazones [69,70], pyrimidinethioles [71-74], substituted thioureas [75-78],

substituted pyridines [79,80], acids [81,82], rhodamine 6G [83-85], thiohydrazides

[86-89], chloride [90], stannous chloride [91], 4,7-diphenyl-1,10-phenanthroline [92],

basic dyes [93], brilliant green [94], quinoxaline dyes [95], 1,10-phenanthroline [96],

3-hydroxy-2-methyl- 1-phenyl-4-pyridone [97], have been reported for

169

spectrophotometric determination of Ru, but most of these reagents lack sensitivity

[63,69,71,76,81,97]. Though the rhodamine 6G is highly sensitive, it tends to form a

precipitate [83] or needs the presence of thiocyanate [84,85] for quantitative

extraction. Alcoholic solutions of reagents [86-89] need to be stored below 150C.

Some reagents need longer heating [62]. There is strong interference [86] from the

metals commonly associated with Ru. The reagent [63] requires the presence of

ethyleneglycol for complex formation. Most of these liquid–liquid extraction

methods require multiple extractions for quantitative recovery of metal, as the

equilibrium distribution is low. A method involving analysis of metals by solid–

liquid separation after liquid–liquid extraction into molten naphthalene for

spectrophotometric determination of metals was developed by Fujinaga and

coworkers [98]. In this method, the liquid–liquid extraction at an elevated

temperature is followed by solid–liquid separation at room temperature. Low-

melting solids such as naphthalene or biphenyl are used as organic solvents for

liquid–liquid extraction of metal chelates at an elevated temperature. The technique

showed improvement in selectivity for the extraction of metal complexes that are

formed at high temperature [99].

The various extraction methods for rhodium describing the nature of the

aqueous phase, organic phase, interference and special features have been

summarized in part 7.2.

The part 7.3 includes the study of extraction of ruthenium(III) with sulphur

containing extractant EBIMTT-I from hydrochloric acid media. The proposed

method is used for rapid and selective extraction of ruthenium(III) from associated

elements from their binary mixtures. It is also tested for the separation and

determination of ruthenium(III) from synthetic mixtures of corresponding alloys.

The part 7.4 includes the study of extraction of ruthenium(III) EBIMTT-I and

EBIMTT-II from hydrochloric acid media. The proposed method is used for rapid

and selective extraction of ruthenium(III) from associated elements in their synthetic

mixtures.

170

7.2 Summary of the methods for solvent extraction of ruthenium(III)

System Aqueous

Phase

Organic

Phase

Interference Special features

N,N-Dailkyl-

N’ benzoyl-

thiourea

pH-3 Solvesso 150 Fe, Cu

Coextracted

i) Coextracted Cu and Fe,

reextracted with 4M H2SO4

[100]

n-Octyl-

aniline

HCl

Toluene/

DIBK/

DIPK

Fe, Co, Ni

coextracted

i) Group extraction for noble

metals.

ii) Noble metals separated

from base metals.

iii) Co extracted metals re-

extracted with suitable

stripping agent.

iv) Method was applicable for

analysis of sludges, floatation

concentrates, rocks and

catalysts etc [101-106]

Petrolium

sulfoxides

3M HCl P-xylene+

decanol

5- hour at

50oC

i) stripping with 10% thiourea

solution.

ii) extraction was less than

80% [107].

Octyl (Phenyl)-

N,N- disobutyl

Carbamoyl

methyl

phosphine

HNO3

0.01-6.0M

Dodecane Pre-

equilibrate

with acid

before

extraction

i) Method suitable for

extraction of actinides and

fission products [108].

Alkylaniline HCl, 1:4 Toluene - i) Method is used for

extraction of noble metals

[109]

171

Tributyl

Phosphate

(TBP)

HNO3

2M

Solvesso-

100

- i) Extraction of Ru in presence

of γ irradiated sulphoxide

ii) Method applied for

extraction of U, Zr and Ru

[110].

Tetra

nitroaniline

HNO3

1%

Tetra nitro-

aniline

Heating

before

extraction at

900

i) Ruthenium was back

stripped with 10%NaOH

ii) Ruthenium was separated

from solution containing

large amount of iridium [111]

Alkylaniline

hydrochloride

HCl

Toluene - i) Method was used for

extraction of PGMS except

osmium and determined by

AAS.

ii) Extraction presence of

petroleum sulphides [112]

Bis(2-

ethylhexyl)

Hydrogen

phosphate

HCl,

pH4.5

Isopar M - i) Method also applicable for

extraction of Rhodium and

Iridium [113].

Cyanex 925 HCl+

SnCl2

Toluene Temperature

dependent

60oC.

i) method applied for the

extraction of real samples

[114].

N,N-Dihexyl

Substituted

amides

HNO3,

3.5 M

n-Dodecane - i) Method was applicable for

extraction of U, Pu, and

fission products [115].

N-butyl–N-

methyl –

Hexananamide

HNO3,

3.5M

n-Dodecane - i) Method was applicable for

extraction of U, Pu, Zr, Eu etc

[116].

172

Calix(4)arenes

bearing mixed

functionalities

HCl Chloroform - i) Possible extraction

mechanism given [117].

Alkylaniline

hydro chloride

HCl, 6M Toluene - i) Extraction in the presence

of petroleum sulphide.

ii) Method was used for

extraction of PGMs, gold in

copper –nickel ore and

related plant materials [118].

P-50 oxime HNO3,

4M

Escaid 100 - i) Method also applicable for

extraction of palladium [119].

Tributyl

Phosphate

(TBP)

HNO3 n-dodecane - i) Ruthenium extracted as

nitrosoruthenium in TBP

[120].

Di(2-

ethylhexyl)

Sulfoxide

(DEHSO)

HNO3 Kerosene - i) The extracting abilities for

U. Th and some fission

products are presented [121].

Octyl

(pheny)-

N,N-

disobutylcar

Bamylmethyl-

phoshine

oxide

(CMPO)

HNO3 Dodecane - i) Extraction in presence of

TBP

ii) Method also applicable for

Pm (III), U(Vi) Pu (IV)

Am(III), Zr (IV), Ru (III),

Fe(III) & Pd(II)

iii) The nature of the species

has been suggested [122].

Trioctylamine HCl, 4M Mixed

Solvent

- i) Synergistic extraction of Ru

(IV) with solvents like TBP,

173

thionyltrifluoro-actone and l-

pheny1-3-methyl1-4-benzoyl-

pyrazolidone -5 [123].

Amino sulfides

and

aminoketo

sulphide

aq. HCl - - i) Maximum extraction of

ruthenium was obtained with

dodecyl sulfide and

pyperidin methyl octyl sufide

[124].

Dihexyl

sulphoxide

HCl P-xylene 2.5 hour

equilibration

time

i) Mechanism of extraction

has been given [125].

5-Cl-2-

hydroxythio-

benzhydrazide

6M HCl Ethyl

alcohol+

molten

napthalene

40 min

heating

i) Ruthenium was determined

from various synthetic

mixtures [126].

Propiconazole 3M HCl Toluene +

decanol

1 hour i) Extraction through ion pair

formation [127].

Trioctylamine

(TOA)

1-7M

HCl

1,2 dichloro

ethane

i) Method used for the

separation of Pd and Ru

[128].

174

7.3 Extraction and spectrophotometric determination of Ruthenium(III) with

EBIMTT-I.

7.3.1 Experimental

General Procedure:

An aqueous solution containing 100μg of ruthenium(III), and enough

hydrochloric acid and water were added so as to give final concentration of 1M with

respect to hydrochloric acid in a total volume of 25ml. The solution was transferred

into a 125 ml separating funnel containing 10 ml of 0.1M extractant in chloroform

and shaken for 30 seconds. After equilibration, the mixture was allowed to separate

and the metal was stripped from the organic phase with two 20 ml portions of

1%NaCl solution. The collected extract was evaporated to moist dryness. The

residue was dissolved in 5ml of concentrated hydrochloric acid to afford a clear

ruthenium(III) solution. It was then estimated spectrophotometrically at 620nm with

pyrimidine-2-thiol [129].

7.3.2 Results and discussion

Effect of solvents:

The extractions were performed from 1M hydrochloric acid medium using

0.1M extractant in various solvents as diluents. Among organic solvents benzene,

chloroform, acetone, carbon tetrachloride, nitrobenzene, isobutyl alcohol, 1-butanol,

isobutyl methyl ketone, ethanol, and N,N dimethylformamide were examined for

the extraction of ruthenium(III) with extractant from hydrochloric acid media,

chloroform medium extracts the complex effectively without third phase formation.

Effect of different acids:

Extraction of ruthenium(III) was carried out in different acid media like

hydrochloric acid, sulphuric acid, nitric acid, acetic acid. The extraction was found to

be quantitative in very high concentration of nitric acid but was incomplete in

sulphuric acid. Hydrochloric acid showed good extraction properties, while nitric

acid forms emulsion at the time of extraction. Due to maximum extraction and better

phase separation hydrochloric acid was found to be appropriate medium for

extraction of ruthenium(III).

175

Effect of acid concentration:

The effect of acid concentration on the extraction of ruthenium(III)-EBIMTT

complex into the organic phase was studied in order to select a suitable

concentration that could be adopted in the determination of ruthenium(III) which

was extracted at different concentration range (0.1-9M) using hydrochloric acid. A

plot between concentration and % extraction has been shown in (Figure 7.3.1). It was

observed that extraction increased with the increase in the acidity of the aqueous

solution and became quantitative at 1M hydrochloric acid. Hence the 1M HCl

solvent system was used for further studies.

Effect of reagent concentration:

Ruthenium (III) was extracted over the 0.5-3 M acidity range with

hydrochloric acid with varying concentrations of EBIMTT. The reagent

concentration was varied from 1×10-5 -2M (Table). It was observed that extraction

increased in the acidity of the aqueous solution and became quantitative at 1M

hydrochloric acid. It was found that 0.1 M reagent in chloroform was needed for

quantitative extraction of ruthenium (III) from 1M hydrochloric acid (Figure 7.3.2).

Effect of shaking time:

This set of experiments was carried out with 1M HCl solutions keeping 100µg

ruthenium (III) concentration, and using a 0.1 M EBIMTT in organic medium. The

time of contact for the two phases varied in between 5 seconds to 10 minutes. It was

found that the extraction kinetics for this system is very fast; an equilibration time of

10 seconds results in a %E of ruthenium (III) almost equivalent to the ones is just

sufficient for quantitative extraction of ruthenium(III) from hydrochloric acid

medium however in a general procedure 30 second of time is recommended in order

to ensure complete extraction of ruthenium (III). Prolonged shaking has no adverse

effect on the efficiency of extraction.

176

Nature of extracted species:

The composition of complex was confirmed by using log D- log C plot. The

graph log D[Ru(III)] versus log C[EBIMTT] at 4M hydrochloric acid was found to be linear

and having slope of 1.42 (Figure 7.3.3). Hence the probable composition of extracted

species in chloroform has been found to be 1:1, [Ru(III): EBIMTT].

Effect of stripping agents:

Ruthenium(III) was stripped with different stripping agents such as mineral

acids, bases, and salts after its extraction. The stripping of ruthenium(III) was

quantitative with 1% NaCl. The stripping was found to be incomplete with ammonia

(40%), and water (60%), with hydrochloric acid (20%), whereas ruthenium(III) was

not stripped with sulphuric acid and sodium hydroxide (Table 7.3.1).

Effect of diverse ions:

The effect of various diverse ions was tested, when ruthenium(III) was

extracted with EBIMTT in chloroform. The tolerance limit of individual diverse ions

was determined with an error less than ±2%. It was observed that the method is free

from interference from a large number of cations and anions (Table 7.3.2). The only

species showing interference in the procedure was Pd(II), Rh(III) and Au(III) ions.

However, the interference due to Pd(II) and Rh(III) was eliminated by masking with

tartarate.

Applications:

The present method was successfully applied for the determination of

ruthenium (III) in a series of synthetic mixtures of various compositions, and also in

a number of alloy samples.

177

Binary separation of ruthenium(III) from iron(III), cobalt(II), nickel(II) and

copper(II):

The method allowed separation and determination of Ruthenium(III) from a

binary mixture containing either iron(III), cobalt(II), nickel(II) and copper(II). In a

typical experiment, solution containing 100μg of ruthenium(III) was taken and

known amounts of other metals were added. The separation of ruthenium(III) from

iron(III), cobalt(II), nickel(II) and copper(II) was accomplished with 0.1M EBIMTT in

chloroform at 1 M hydrochloric acid. Under these conditions all the base metals

remains in the aqueous phase and these base metals determined

spectrophotometrically with thiocynate [130], 1-nitroso-2 napthol [130], DMG [130]

and pyrimidine-2-thiol [131] respectively. Ruthenium (III) was stripped from the

organic phase with 50 ml 2% NaCl solution. The extract was evaporated to moist

dryness and leached with 1M hydrochloric acid to form the clear solution.

Ruthenium(III) was estimated spectrophotometrically by stannous chloride method.

The recovery of ruthenium(III) and that added ions was 99.5% and results are

reported in (Table 7.3.3).

Separation of ruthenium (III) from synthetic mixtures:

In its natural occurrence ruthenium is always associated with the noble and

base metals; hence its separation from these metals is of great importance. The

proposed method allows the selective separation and determination of ruthenium

from many metal ions. Synthetic mixtures corresponding to alloys were prepared

and analyzed for ruthenium(III) content. Ruthenium(III) was recovered

quantitatively from hydrochloric medium by the proposed method. The method is

selective and permits rapid separation and determination of micro amounts of

ruthenium(III). The average recovery of ruthenium(III) was found to be 99.5% (Table

7.3.4).

178

Separation of ruthenium(III) from alloys:

The extraction study showed that it is possible to separate ruthenium(III)

from platinum(IV), palladium(II), gold(III), and the base metals from one another.

Under the optimum conditions of separation for ruthenium(III), there is quantitative

extraction of platinum (IV), palladium(II) and gold(III), and the base metals. Hence,

the separation can be achieved by the use of different stripants. The extraction

scheme is presented in the form of a flow sheet (Scheme 7.1). Real samples were not

available at the working laboratory, which forced us to use synthetic mixtures

containing ruthenium(III), platinum(IV), palladium(II), gold(III), and the base metals

corresponding to the various alloys (Table 7.3.5).

179

Table 7.3.1 Effect of different stripping agents on stripping of ruthenium (III)

Stripping agent Concentration Extraction (%)

HCl Concentrated (2×10 ml) 80

NH3 Concentrated (2×10 ml) 20

NaOH 1 mol.dm-3 (2×5 ml) -

H2O Double distilled water 77

NaCl 2% (2×10 ml) 99.9

Na2CO3 +NaHCO3 pH 9 (2×10 ml) 11

Table 7.3.2 Effect of foreign ions added on extraction of ruthenium (III) with

EBIMTT-I

Ions added Tolerance limit (mg) Ions added Tolerance limit (mg)

Cu(II) 5 Mo(VI) 20

Ni(II) 5 W(VI) 20

Co(II) 10 Au(III) 0.5

Pb(II) 15 Pt(IV) 0.5

Mn(II) 10 Rh(III) 0.5

Zn(II) 15 Pd(II) 0.5

Cd(II) 15 Fluoride 100

Hg(II) 15 Bromide 100

Sn(II) 15 Chloride 100

Fe(III) 15 Nitrate 100

Cr(III) 15 Sulphate 100

Bi(III) 10 Tartarate 100

Ca(II) 20 Citrate 100

Ce(IV) 10 Acetate 100

Th(IV) 10 Phosphate 100

Zr(IV) 10 EDTA 100

180

Table 7.3.3

Binary separation of Ruthenium(III) from base metals

Composition of metal

ions(µg)

Average % recovery* Ru(III) R.S.D. (%)

Ru(III) 100;Fe(III)15000 99.8 0.19

Ru(III) 100;Co(II)10000 99.2 0.20

Ru(III) 100;Cu(II)5000 99.4 0.23

Ru(III) 100;Ni(II)5000 99.0 0.22

*Average of six determination.

Table 7.3.4

Analysis of synthetic mixtures containing ruthenium (III) with EBIMTT-I

Composition Ruthenium

found (μg)*

Recovery

(%)

R.S.D

(%)

Ru(III)100+Pd(II) 500 98.6 99.2 0.17

Ru(III)100+Au(III) 500 97.8 98.1 0.25

Ru(III)100+Pt(IV) 500 97.7 98.4 0.23

Ru(III)100+Rh(III) 500 98.8 99.4 0.14

Ru(III)100+Pd(II)500+Rh(III)200 97.9 98.5 0.23

Ru(III)100+Pd(II)500+AuIII)200 97.7 98.4 0.14

Ru(III)100+Pt(IV)500+AuIII)200 97.7 98.4 0.14

Ru(III)100+Pt(IV)500+Pd(II)200+Au(III)200 97.6 98.5 0.23

Ru(III)100+Pt(IV) 200+Pd(II) 200+Rh(III)

200+Au(III) 200 +Co(II)200

98.7 99.4 0.15

*Average of six determination.

181

Table 7.3.5

Analysis of alloys containing ruthenium(III) with EBIMTT-I

Alloy Composition

(%)

Ru (III)

taken (µg)

Ru(III)

found(µg)

Recover*

(%)

R.S.D

(%)

Pt-Ru alloy Ru 5, Pt 95 50 49.7 99.6 0.2

Jewelry alloy Ru 4,Pd 95,Rh 1 50 49 99 0.4

Osmiridium

alloy

Ru 8, Os 32, Ir 45,Pt

10,Rh 11,Au1

50 49.8 99.7 0.2

Fig 7.3.1 Extraction of Ru(III) as a function of Hydrochloric acid concentration

182

Fig 7.3.2 Extraction of Ruthenium(III) as a function of EBIMTT concentration

Fig 7.3.3 Log-log plot of distribution ratio (DRu) versus EBIMTT-I concentration at

4 mol/dm3 HCI

183

7.4 Extraction and spectrophotometric determination of Ruthenium (III) with

EBIMTT II:

7.4.1 Experimental

Procedure:

The liquid-liquid extraction and the spectrophotometric method followed for the

determination of the metal ions was the same as described in 7.3.1 of this chapter.

7.4.2 Results and discussion

Effect of diverse ions:

The effect of various diverse ions was tested, when ruthenium(III) was

extracted with EBIMTT in chloroform. The tolerance limit of individual diverse ions

was determined with an error less than ±2%. It was observed that the method is free

from interference from a large number of cations and anions (Table 7.4.1). The only

species showing interference in the procedure were Pd(II), Rh(III) and Au(III).

However, the interference of Pd (II) and Rh(III) was eliminated by masking with

tartrate.

Applications:

The present method was successfully applied for the determination of

ruthenium (III) in a series of synthetic mixtures of various compositions, and also in

a number of alloy samples.

Binary separation of ruthenium(III) from iron(III), cobalt(II), nickel(II) and

copper(II):

The method allowed separation and determination of ruthenium(III) from a

binary mixture containing either iron(III), cobalt(II), nickel(II) and copper(II). In a

typical experiment, solution containing 100μg of ruthenium (III) was taken and

known amounts of other metals were added. The separation of ruthenium (III) from

iron(III), cobalt(II), nickel(II) and copper(II) was accomplished with 0.1 M EBIMTT II

in chloroform at 1M hydrochloric acid. After stripping from organic layer ruthenium

(III) was estimated spectrophotometrically by stannous chloride method (Table

7.4.2).

184

Conclusions:

We have reported here the use of EBIMTT-I and EBIMTT-II as extractants for

ruthenium (III) from hydrochloric acid medium. On the basis of extraction studies

performed, it was observed that both the extractants contains ‘S’ as a donor atom

which is very selective and effective. EBIMTT-I having the oxygen containing side

chain is more effective than EBIMTT-II.

The effectiveness of extractants has been evaluated for ruthenium(III) from

variety of ruthenium bearing materials. The important feature of this method

includes selective separation of ruthenium(III) from other platinum group metals

and base metals which are generally associated with it. It is free from interference

from a large number of foreign ions, low reagent concentration is required and time

needed for equilibration is very short, (about 30 seconds).

185

Table 7.4.1

Effect of foreign ions added on extraction of ruthenium (III) with EBIMTT-II

Ions added Tolerance limit (mg) Ions added Tolerance limit (mg)

Cu(II) 5 Rh (III) 0.5

Ni(II) 5 Pd (II) 0.5

Co(II) 10 Chloride 100

Fe(III) 15 EDTA 100

Au(III) 0.5 Sulphate 50

Pt(IV) 0.5 Acetate 100

Table 7.4.2

Analysis of synthetic mixture of ruthenium(III) with EBIMTT II

Composition Ruthenium

found (μg)

Recovery*

(%)

R.S.D.

(%)

Ru(III)100+Pd(II)500 98.0 99.0 0.17

Ru(III)100+Au(III)500 97.8 98.9 0.22

Ru(III)100+Pt(IV)500 98.2 99.1 0.21

Ru(III)100+Rh(III)500 98.0 99.0 0.24

Ru(III)100+Pt (IV)200+Pd(II)

200+Rh(III)200+Au(III)200+Co(II)200

97.6 98.8 0.23

*Average of six determination.

186

Separation scheme (flow sheet)*

Ru(III) + Rh(III) +Au(III) + Fe(III) + Co(II) + Ni(II) + Cu(II)

Adjust the acidity to 1M with HCl in a total volume of 25 ml and extract with 10 ml of 0.1 M

EBIMTT in chloroform for 30 second

Aqueous phase Organic phase

Fe(III)+Co(II) +Ni(II)+Cu(II) Ru(III)+Rh(III) +Au(III)

Dilute the organic phase with 20 ml

chloroform strip with 1% NaCl

Aqueous phase Organic phase

Ru(III) determine with Rh(III)+Au(III)

Pyrimidine-2-thiol Stripping agents

5M HCl 1:1 aqueous ammonia

Rh(III) Au(III)

* Ru(III), 100 mg + Rh(III) 100 mg +Au(III) 100 mg + 2000 mg each of Fe(III) + Co(II) +

Ni(II) + Cu(II)

Scheme: 7.1 Separation scheme (flow sheet)

187

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