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Extraction of Cerium(IV) with Versatic 911 &Its Separation from Lanthanide Elements
u. S. RAy* & S. c. MODAK
Department of Chemistry, Visva-Bharati, Santiniketan 731 235
Received 3 December 1980; revised and accepted 22 January1981
A rapid and selective method for the extraction and separationof Ce(IV) with liquid cation exchanger, Versatic 911, in benzenehas been developed. The distribution coefficient (D) of Ce(IV)with Versatic 911 between the organic and the aqueous phasesshows high values (248 to 497.5) in the pH range 5.1-5.6. Theeqnilibration between the two phases is achieved within 1 min.The species extracted in the organic phase contains Ce(IV) andthe extractant in the ratio 1 : 4. Ce(IV) has been quantitativelyseparated from various binary and synthetic mixtures containingrare earth elements.
VERSATIC acids, viz. Versatic 911, Versatic 10etc. and naphthenic acid have been shown to
be promising extractants for large scale hydro-metallurgical processing of divalent transitionmetals=", The compositions of the extracted speciesof several metals using Versatic 911 were investi-gated by several workers=". However, no systematicattempt has yet been made to study the extractionof cerium(IV) with Versatic 911, and hence thetitle investigation. The probable composition ofthe extracted species has also been determined.
Versatic 911 (Shell Chemical Co., London)" isa mixture of C9-Cll aliphatic mono carboxylic acidshaving the general structure (R1R2)C(CHs)COOHwhere R1, R2 are Cs-, Cc chain, was used in con-junction with benzene without further purification.The purity and concentration of Versatic 911 was99 % and 5.43M respectively''.
Ceric sulphate solution (3.75 mg/ml) was preparedas follows : Ce(S04)2. 4H20 (Chemapol,Czechoslovakia) (3g) was dissolved in doubly deio-nised water (200 ml) and to this was added concen-trated H2S04 (AR, 20 ml). The solution wasstandardized by the complexometric titration withEDTA using xylenol orange indicator". Ascorbicacid (BDH, AR) was used for the reduction of Ce(IV)during estimation. All other chemicals and solventsused were of analytical grade.
Buffer solutions of different pH values were pre-pared from 1M sodium acetate solution and the pHadjusted using chloroacetic acid (pH 1.5 to 2.5)and glacial acetic acid (pH 3.5 to 6).
General procedure - An aliquot (2 ml) of thetest solution containing 7.5 mg of the metal ionwas mixed with the appropriate buffer solution(10 ml). In experiments involving diverse ions,the foreign ions were added before the buffer solu-tions were introduced. The pH of the solution wasadjusted and equilibrated with Versatic 911 (10 ml)for 5 min, using benzene as diluent (solvent :diluent, 1:5). In each case the volume of theaqueous phase was made upto 20 ml and that of theorganic phase 10 ml. The ultimate concentrationof cerium (IV) in the aqueous phase was 2.6 X
NOTES
10-3M and that of Versatic 911 was 0.905 M. Theequilibration time was varied from 0.5-10 min andit was found that the distribution coefficient reacheda constant value within 1 min. However, the equili-bration time was fixed at 5 min. All the extractionexperiments were carried out at 300' ± 1"C. Thetwo phases were allowed to settle for 10 min, theaqueous phase separated and the equilibrium pHmeasured. To remove any trace of organic solvententrained in the aqueous phase, the latter waswashed with benzene (5 ml). The resulting benzeneextract was mixed with the separated organic phase.The amount of metal ion present in the aqueousphase was estimated by complexometric titrationwith EDTA. The metal ion in the organic phasewas stripped with 2N HN03 (20 ml) for 10 min.After back extraction the phases were allowed tosettle for 10 min, the aqueous phase (acid extract)separated and again shaken with benzene (5 ml)to remove any entrained solvent present in theaqueous phase. Finally the metal ion present inthe aqueous phase was estimated. This recommendedprocedure was followed except for the variationindicated.
pH : The extraction of cerium(IV) with Versatic911 at various pHs was performed using buffersolutions of different pHs. The effect of varyingpH on the extraction of Ce(IV) was investigatedand it was observed that the extraction of Ce(IV)increased with increased pH of the aqueous phaseand became quantitative at pH 5.1-5.6. Cerium(IV)was found to undergo hydrolysis at higher pH asrevealed by carrying out the extraction in the pre-sence of 1M acetate. For all quantitative extractionsthe pH of aqueous phase was maintained at 5.1.
Various diluents, viz. carbon tetrachloride, ben-zene, toluene, xylene, diisopropyl ether, chloroformand butanol were tried, keeping the ratio of organicto aqueous phase at 1:2. Quantitative extractionof Ce(IV) was achieved in most of the cases. How-ever, benzene was the most suitable diluent and wasused in all the experiments.
The contact time was varied from 30 see to 10min. The distribution coefficient reached a constantvalue within 1 min of shaking and back extractionwas completed within 5 min. Contact time andstripping time was kept 5 min in all the experiments.20 ml of 2N nitric acid was used for stripping ceriumfrom the organic phase.
The effect of solvent concentration on extractionwas studied by varying Versatic 911 concentrationfrom 1.086 X 10-1 M to 3.4 X 10-3 Musingbenzene diluent at pH 5.1, metal concentration =(2.3 X 10-3 M) and constant acetate concentration.Increase in extractant concentration led to increasedextraction of Ce(IV), a linear relationship withslope = 2 was observed between log D and log[Versatic 911]. Versatic 911 in benzene diluentsexists as dimer", Bearing this in mind and onthe basis of the results obtained, the stoi chiometryof Cerium (IV) extracted by Versatic 911 dilutedwith benzene can be presented as :
CeH + 2R2H2 :r!: CeR4 + 4H +where R2H2 represents the dimeric form of Versatic
935
INDIAN J. CHEM., VOL. 20A, SEPTEMBER 1981
TABLE 1 - EFFECT OF FOREIGN IONS ON THE EXTRACTIONOF CERlUM(IV)
[Amount of Ce(IV) taken = 7.5 mg]
Foreign ions Amount taken Ce(IV) found(mg)
10.0 7.3710.0 7.4110.0 7.2210.0 7.4110.0 7.4110.0 7.4710.0 7.6515.0 7.608.0 7.47
10.0 7.485.0 7.475.0 7.47
10.0 7.41
Mg'·Cas+Co!+Znl+CdHLa3+Pr'"Nd'+Sm3+Gd3+Dy3+TbO+Hg'+
Errorco-1.73-1.17-3.73-1.17-1.17-0.39+2.00+1.33-0.39-0.26-0.39-0.39-1.17
TABLE2 - EXTRAcnON OF CERIUM (IV) FROM SYNTHETICMIXTURES
[Amount of Ce(lV) taken ~ 7.5 mg]
Synthetic mixture. Mixture of Ce(IV) with
Ce(JV) found(mg)
7.447.487.487.467.427.527.527.50
Tb(m) + Dy(DI)DyClII) + Gd(lll)Pr(JII) + Gd(III)Nd(III) + Gd(lll)Pr(III) + Nd(III)La(lIl) + Pr(IIJ) + Nd(lIl)La(III) + Sm(JII) + Gd(III)Zn(II) + Cd(II) + HgIII)
Errorco
-0.8-0.2-0.2-0.5-1.0+0.2+0.2
o
911 in benzene and the barred species are in theorganic phase.
Interference - It was also observed that theamount of foreign ions coextracted with Ce(IV) wasnegligible in most of the cases (see Table I). Cerium(IV) could be separated from lanthanum, praseo-dymium, neodymium, samarium, gadolinium; dys-prosium, terbium, mercury and lead. The presenceof magnesium, calcium, cobalt, zinc and cadmiumdid not interfere in the extraction of cerium. Theinterfering ions were iron, nickel, copper, thoriumand uranium.
Separation of cerium(IV) from synthetic mixture-The recommended procedure for the extraction ofCe(IV) was applied to several synthetic mixtures,produced by mixing 5 mg of each metal ion. Thetotal volume of the aqueous phase was kept 20 mland extracted with 0.905M Versatic 911 (10 mlin benzene. Extractions were carried out at pH 5.1using suitable buffer solution. The results given inTable 2 show that in most of the cases quantitativerecovery of Ce(IV) was achieved. The proposedmethod can therefore be applied for selective extrac-tion and separation of ee(IV) from rare earthmixtures.
One of the authors (S.C.M.) is thankful to theUGC, New Delhi for the award of a junior researchfellowship and to Shell Chemical Co. (London) forthe gift sample of Versatic 911.
936
References1. GINDIN, L. M., BOBIKov, P. I., KOUBA,E. F. & BUGAEVA,
A. V., Russ. J. inorg. Chern.,5 (1960), 1146.2. FLETT, D. S. & JAYCOCK,M. J., Ion exchange and solvent
extraction, Vol. 3 (Marcel Dekker, New York), 1973, 1.3. 5mBATA, J., IZUTANl, M. KIROKI, K. & NIsmMURA, S.,
Nippon Kinzoku Gakkaishi, 38 (1974), 847 : Chern.Abstr., 82 (1975), 336585 S.
4. SHIBATA,J. & NIsmMURA, S., Nippon Kinzoku Gakkaishi,3!J (1975), 206 : Chern. Abstr., 82 (1975), 127877 q.
5. RAY, U. S. & MODAK, S. C., Separ. Sci. & Tech., 16(1981), 87.
6. RAY, U. S. & MODAK, S. C., J. Indian chem. Soc., 58(1981),38
7. ASHBROOK,A. W., J. inorg. nuc/. Chem., 34 (1972), 1721.8. PRIBIL RUDOLF, Chelometry=-basic determinations (Cherna-
pol. Czechoslovakia), 1961.
Extraction of Co(II) with Dipbenylcarbazone inPresence of Pyridine, ~-Picoline & Quinoline
BINA GUPTA, J. M. SINGH & S. N. TANDON·Department of Chemistry, University of Roorkee,
Roorkee 247 672
Received 1 November 1980; revised and accepted 4 December1980
The synergistic effect of the bases like pyridine, ~-picolineand quinoline in the extraction of Co(II)-DPC complex variesin the order : pyridine > ~-picoline > quinoline. The speciesextracted has been identified by the slope analysis method andextraction constants have been calculated.
IN continuation of our earlier work! on thesynergism in the extraction of Zn(II) and Cd(II)
diphenylcarbazone (DPC) complexes in non-polarsolvents in the presence of nitrogen containing or-ganic bases, the present note reports the synergisticeffect of the title bases in the extraction of Co(II)-DPC complex. The metal-DPC-base species hasbeen identified by the slope analysis method.
Cobalt sulphate (AR) was dissolved in. doublydistilled water and the solution standardised by theusual method. A freshly prepared solution ofdiphenylcarbazone in benzene was always used. Theorganic bases viz. pyridine, ~-picoline and quino-line were of AR grade and used as such. 5PCOradio-isotope (carrier-free, Bhabha Atomic ResearchCentre) was used for distribution studies. At around55% extraction the values show a precision of±l%.
In each set equal volumes (10 ml) of the aqueousphase (1.0 x 1O-4M metal ion) and organic phase(0.5 x 10-2M or any other concentration of DPC inbenzene) were mixed and shaken at room tempera-ture (30±2°C) for 30 min for complete equili-bration. After equilibration the two phases wereseparated and pH of the aqueous phase measured.Suitable aliquots of the two phases were pipetted outand counted using a well-type NaI(Tl) scintillationcounter.
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