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Solvent extraction of indium (III) by LIX 973N
Hydrometallurgy 51 Ž1999. 97–102
Solvent extraction of indium žIII / by LIX 973N F.J. Alguacil (CSIC), AÕda. Gregorio del Amo 8, Ciudad UniÕersitaria, Centro Nacional de InÕestigaciones Metalurgicas ´ 28040 Madrid, Spain Received 6 June 1998; revised 8 October 1998; accepted 10 October 1998
Abstract The use of LIX 973N for extraction of indium ŽIII. from sulphate media is studied. The extraction system is studied as a function of equilibration time, temperature, diluent and metal and extractant concentrations. Experimental data have been analyzed graphically and numerically to determine the stoichiometry of extracted species and their equilibrium constants. It was found that indium was extracted into the organic phase by formation of the InR 3 species Žlog K ext s y7.7 Žgraph.., log K ext s y8.27 " 0.04 Žnum.... The effect of aqueous ionic strength on indium extraction was also studied. q 1999 Published by Elsevier Science B.V. All rights reserved. Keywords: Indium ŽIII.; Solvent extraction; LIX 973N
1. Introduction The use of the leaching-solvent extraction–electrowinning circuit has produced the most economical copper in the world. As extractant for copper, oximes are used; to improve the extraction abilities, new oximes have been and are being introduced to the market and especially oxime mixtures based on combinations of the basic components salicylaldoximes and ketoximes, which blended at various ratios result in extractants of variable extractive strength. One of these is LIX 973N, about which little is known. On the other hand, other metals are suitable for extraction by these reagents but data have been normally overwhelmed by information relating to copper and to a lesser extent nickel and cobalt. A number of these metals are responsible for environmental pollution or need to be eliminated in the circuits of production of other metals, thus new approaches are constantly open to the use of these oximes. One of these metals is indium. Indium was considered a valuable metal a number of years ago and the use of solvent extraction for 0304-386Xr99r$ - see front matter q 1999 Published by Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 3 8 6 X Ž 9 8 . 0 0 0 7 2 - 3
98
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
its separationrrecovery was fully considered, however, actually indium can be considered either an impurity in a number of processes or a toxic element that needs to be eliminated. Solvent extraction reagents for indium have been based on acidic, amines and solvation reagents w1–5x, and only recently the use of oximes for the extraction of indium has been considered w6x. The present work investigates the behaviour of LIX 973N oxime for the extraction of indium ŽIII. from aqueous sulphate solutions. Experimental data have been analyzed both graphically and numerically in order to determine the stoichiometry of extracted species and the equilibrium constants. Comparative data on the extraction of indium ŽIII. from nitrate, chloride and sulphate aqueous media are also reported.
2. Experimental LIX 973N ŽHenkel. reagent is a mixture of 5-dodecyl-salicylaldoxime and 2-hydroxy-5-nonylacetophenone oxime, the reagent also contains a modifier Žtridecanol.; 5-dodecyl-salicylaldoxime is the main component of the mixture w7x. The extractant was used as supplied by the manufacturer. The approximate active substance concentration in the organic solutions was determined by the ultimate loading. All other chemicals were of AR grade. Extractions were carried out by shaking equal volumes of the appropriate organic and aqueous solutions in separatory funnels, for the time and at the temperature required. Indium was analyzed by AAS.
3. Results and discussion Experiments on the influence of contact time and temperature on indium extraction have been carried out by shaking at 208C for various lengths of time aqueous solutions of 0.1 grl indium and organic solutions of 5% vrv LIX 973N in xylene at OrA ratio of 1. Results obtained showed that equilibrium is achieved within 20 min of contact Ž56.5% extraction at pH eq of 3.82.. The relationship between indium extracted into the organic phase and the temperature was also studied; the aqueous and organic solutions used being the same as above. Fig. 1 shows the variation of log D In against 1000rT; in the range of temperatures used there is an increase of indium extraction with increase of temperature. From these data is obtained D H8 s 21.1 kJrmol, the extraction is endothermic. The performance of the LIX 973N-indium extraction system was studied using xylene or n-decane as diluents for the organic phase. Aqueous solutions contained 0.1 grl indium whereas the organic phases were of 10% vrv LIX 973N in each diluent. Other experimental conditions were temperature 208C, equilibration time 10 min and OrA ratio 1. The results obtained shown that the change of the diluent only slightly influences indium extraction since the pH 50 values vary from 3.49 Žxylene. to 3.57 for n-decane.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
99
Fig. 1. Arrhenius plot for the extraction of In by LIX 973N. Temperature 208C. Equilibration time 20 min. Equilibrium pH 3.8"0.05. Dotted line shows 95% confidence interval.
The effect of the initial indium and extractant concentrations on metal extraction was examined. Experiments were carried out at 208C by contacting aqueous solutions which contained various indium concentrations and organic phases of 5–10% vrv LIX 973N in xylene. Fig. 2 shows that the variation of the initial indium concentration has negligible influence on the pH 50 value. This independence indicates that apparently there is no formation of polynuclear indium species in the organic phase.
Fig. 2. Indium extraction by LIX 973N at various initial metal and extractant concentrations. Equilibration time 20 min. OrA ratio 1. LIX 973N 10% vrv Žfilled., LIX 973N 5% vrv Žunfilled..
100
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
The results also show that the variation in the initial LIX 973N concentration has an influence on indium extraction. The increase in the extractant concentration shifts the extraction curve to the left as expected from the general extraction reaction shown below. Metal extraction by oximes, and even oxime mixtures, can be described by various equilibria, the most simple approach is by the following reaction: nq q nHR org ° MR n org q nHq M aq aq
Ž 1.
In the present study, and assuming ideal behaviour for the above reaction in the organic and aqueous phases, the following expression is obtained for the indium distribution coefficient as a function of the oxime concentration and the equilibrium pH: log D indium s log K ext q n Ž log w HR x org q pH eq .
Ž 2.
where K ext is the extraction constant derived from Eq. Ž1.. The coefficient n has been evaluated by plotting log D In vs. Žlog wHRxorg q pH eq .; Fig. 3 shows the result obtained. The slope can be assumed 3, thus the extracted species has the probable stoichiometry of InR 3 ; from this plot is also obtained log K ext s y7.7. Experimental data were also analyzed numerically by the program LETAGROPDISTR w8x in order to define the species extracted in the organic phase and the value of log K ext . Several models with species of various stoichiometries were tried in order to investigate the possibility of finding different species which could improve the fit to the experimental data. For this particular system, the program fits the existence of one species in the indium-loading organic solution; the corresponding stoichiometry is represented by InR 3 . Table 1 summarizes the results of the graphical and numerical
Fig. 3. Plot of log D In vs. Žlog wHRx org qpH eq .. Initial metal concentrations 0.025 to 0.1 grl. Initial LIX 973N concentrations 5 to 10% vrv in xylene.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
101
Table 1 Equilibrium constant for the extraction of In by LIX 973N Species
log K ext Žgraphical.
log K ext Žnumerical.
s Žlog K ext .
U
s
InR 3
y7.7
y8.27"0.04
0.01
0.22
0.08
calculations. This stoichiometry agrees well with that reported using Cyanex 301 and LIX 984 extractants w3,6x. Furthermore, various tests were carried out in order to determine the influence of the aqueous ionic media on the extraction of In ŽIII. by LIX 973N at a constant ionic strength of 0.5 M. As seen in Fig. 4, in which the percentage of indium extraction vs. pH eq is represented, the extraction efficiency follows the order nitrate 4 chlorides sulphate. The presence of chloride ions in the aqueous solution do not enhance indium extraction as has been shown earlier w4x; indium ŽIII. forms stable complexes with chloride and sulphate ions which possibly compete with the oxime in the extraction of the metal. On the other hand, the presence of nitrate anion, Žwhich forms only very weak nitrate complexes with indium ŽIII.., in the aqueous solution significantly influences the extraction of indium by LIX 973N with respect to the extraction of the metal from aqueous solutions of near zero ionic strength ŽFig. 4.. This indicates that the presence of this anion in the aqueous solution produces a salting-out effect, which could be tentatively interpreted by the use of activity coefficients and appropriate modelling, e.g., SIT, Davies model, etc.
Fig. 4. Percentage of extraction of indium by LIX 973N from various ionic media as a function of the equilibrium pH. Aqueous phase: 0.1 grl In. Organic phase: 5% vrv LIX 973N in xylene. Temperature 208C. Equilibration time 20 min. OrA ratio 1.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
102
4. Conclusions The results obtained show that the commercially available extractant LIX 973N can be used as a reagent for indium extraction in sulphate media at moderate acidic pH values and low aqueous ionic strength. The extraction reaction is endothermic Ž D H8 s 21.1 kJrmol. and is dependent on the aqueous pH and the extractant concentration. The extraction of indium proceeds by a cation exchange reaction, indium is extracted into the organic phase by the formation of a single species of probable stoichiometry InR 3 with log K ext s y8.27 " 0.04 Žnum... No polynuclear indium complexes are formed in the experimental conditions used. The efficiency of the indium extraction is strongly dependent on the counter-anion Žchloride, sulphate, nitrate. present in the aqueous solution.
Acknowledgements To the CSIC ŽSpain. for support to carry out this work.
References w1x w2x w3x w4x w5x w6x w7x w8x
G.M. Ritcey, A.W. Ashbrook, Solvent Extraction, Part II, Elsevier, Amsterdam Ž1979., p. 556. S. Amer, Rev. Met. 17 Ž2. Ž1981. 109. M. Avila Rodriguez, G. Cote, D. Bauer, Solvent Extr. Ion Exch. 10 Ž5. Ž1992. 811. S. Facon, M. Avila Rodriguez, G. Cote, D. Bauer, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 1, SCI-Elsevier Applied Science, London Ž1993., p. 557. M.A. Karve, S.M. Khopar, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 3, SCI-Elsevier Applied Science, London Ž1993., p. 1347. E. Rodriguez de San Miguel, J.C. Aguilar, J.P. Bernal, M.L. Ballinas, M.T.J. Rodriguez, J. de Gyves, K. Schimmel, Hydrometallurgy 47 Ž1997. 19. Ž1997.. Henkel KGaA, LIX 973N Material Safety Data Sheet, Dusseldorf ¨ D.H. Liem, Acta Chem. Scand. 25 Ž1971. 1521.
Solvent extraction of indium žIII / by LIX 973N F.J. Alguacil (CSIC), AÕda. Gregorio del Amo 8, Ciudad UniÕersitaria, Centro Nacional de InÕestigaciones Metalurgicas ´ 28040 Madrid, Spain Received 6 June 1998; revised 8 October 1998; accepted 10 October 1998
Abstract The use of LIX 973N for extraction of indium ŽIII. from sulphate media is studied. The extraction system is studied as a function of equilibration time, temperature, diluent and metal and extractant concentrations. Experimental data have been analyzed graphically and numerically to determine the stoichiometry of extracted species and their equilibrium constants. It was found that indium was extracted into the organic phase by formation of the InR 3 species Žlog K ext s y7.7 Žgraph.., log K ext s y8.27 " 0.04 Žnum.... The effect of aqueous ionic strength on indium extraction was also studied. q 1999 Published by Elsevier Science B.V. All rights reserved. Keywords: Indium ŽIII.; Solvent extraction; LIX 973N
1. Introduction The use of the leaching-solvent extraction–electrowinning circuit has produced the most economical copper in the world. As extractant for copper, oximes are used; to improve the extraction abilities, new oximes have been and are being introduced to the market and especially oxime mixtures based on combinations of the basic components salicylaldoximes and ketoximes, which blended at various ratios result in extractants of variable extractive strength. One of these is LIX 973N, about which little is known. On the other hand, other metals are suitable for extraction by these reagents but data have been normally overwhelmed by information relating to copper and to a lesser extent nickel and cobalt. A number of these metals are responsible for environmental pollution or need to be eliminated in the circuits of production of other metals, thus new approaches are constantly open to the use of these oximes. One of these metals is indium. Indium was considered a valuable metal a number of years ago and the use of solvent extraction for 0304-386Xr99r$ - see front matter q 1999 Published by Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 3 8 6 X Ž 9 8 . 0 0 0 7 2 - 3
98
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
its separationrrecovery was fully considered, however, actually indium can be considered either an impurity in a number of processes or a toxic element that needs to be eliminated. Solvent extraction reagents for indium have been based on acidic, amines and solvation reagents w1–5x, and only recently the use of oximes for the extraction of indium has been considered w6x. The present work investigates the behaviour of LIX 973N oxime for the extraction of indium ŽIII. from aqueous sulphate solutions. Experimental data have been analyzed both graphically and numerically in order to determine the stoichiometry of extracted species and the equilibrium constants. Comparative data on the extraction of indium ŽIII. from nitrate, chloride and sulphate aqueous media are also reported.
2. Experimental LIX 973N ŽHenkel. reagent is a mixture of 5-dodecyl-salicylaldoxime and 2-hydroxy-5-nonylacetophenone oxime, the reagent also contains a modifier Žtridecanol.; 5-dodecyl-salicylaldoxime is the main component of the mixture w7x. The extractant was used as supplied by the manufacturer. The approximate active substance concentration in the organic solutions was determined by the ultimate loading. All other chemicals were of AR grade. Extractions were carried out by shaking equal volumes of the appropriate organic and aqueous solutions in separatory funnels, for the time and at the temperature required. Indium was analyzed by AAS.
3. Results and discussion Experiments on the influence of contact time and temperature on indium extraction have been carried out by shaking at 208C for various lengths of time aqueous solutions of 0.1 grl indium and organic solutions of 5% vrv LIX 973N in xylene at OrA ratio of 1. Results obtained showed that equilibrium is achieved within 20 min of contact Ž56.5% extraction at pH eq of 3.82.. The relationship between indium extracted into the organic phase and the temperature was also studied; the aqueous and organic solutions used being the same as above. Fig. 1 shows the variation of log D In against 1000rT; in the range of temperatures used there is an increase of indium extraction with increase of temperature. From these data is obtained D H8 s 21.1 kJrmol, the extraction is endothermic. The performance of the LIX 973N-indium extraction system was studied using xylene or n-decane as diluents for the organic phase. Aqueous solutions contained 0.1 grl indium whereas the organic phases were of 10% vrv LIX 973N in each diluent. Other experimental conditions were temperature 208C, equilibration time 10 min and OrA ratio 1. The results obtained shown that the change of the diluent only slightly influences indium extraction since the pH 50 values vary from 3.49 Žxylene. to 3.57 for n-decane.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
99
Fig. 1. Arrhenius plot for the extraction of In by LIX 973N. Temperature 208C. Equilibration time 20 min. Equilibrium pH 3.8"0.05. Dotted line shows 95% confidence interval.
The effect of the initial indium and extractant concentrations on metal extraction was examined. Experiments were carried out at 208C by contacting aqueous solutions which contained various indium concentrations and organic phases of 5–10% vrv LIX 973N in xylene. Fig. 2 shows that the variation of the initial indium concentration has negligible influence on the pH 50 value. This independence indicates that apparently there is no formation of polynuclear indium species in the organic phase.
Fig. 2. Indium extraction by LIX 973N at various initial metal and extractant concentrations. Equilibration time 20 min. OrA ratio 1. LIX 973N 10% vrv Žfilled., LIX 973N 5% vrv Žunfilled..
100
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
The results also show that the variation in the initial LIX 973N concentration has an influence on indium extraction. The increase in the extractant concentration shifts the extraction curve to the left as expected from the general extraction reaction shown below. Metal extraction by oximes, and even oxime mixtures, can be described by various equilibria, the most simple approach is by the following reaction: nq q nHR org ° MR n org q nHq M aq aq
Ž 1.
In the present study, and assuming ideal behaviour for the above reaction in the organic and aqueous phases, the following expression is obtained for the indium distribution coefficient as a function of the oxime concentration and the equilibrium pH: log D indium s log K ext q n Ž log w HR x org q pH eq .
Ž 2.
where K ext is the extraction constant derived from Eq. Ž1.. The coefficient n has been evaluated by plotting log D In vs. Žlog wHRxorg q pH eq .; Fig. 3 shows the result obtained. The slope can be assumed 3, thus the extracted species has the probable stoichiometry of InR 3 ; from this plot is also obtained log K ext s y7.7. Experimental data were also analyzed numerically by the program LETAGROPDISTR w8x in order to define the species extracted in the organic phase and the value of log K ext . Several models with species of various stoichiometries were tried in order to investigate the possibility of finding different species which could improve the fit to the experimental data. For this particular system, the program fits the existence of one species in the indium-loading organic solution; the corresponding stoichiometry is represented by InR 3 . Table 1 summarizes the results of the graphical and numerical
Fig. 3. Plot of log D In vs. Žlog wHRx org qpH eq .. Initial metal concentrations 0.025 to 0.1 grl. Initial LIX 973N concentrations 5 to 10% vrv in xylene.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
101
Table 1 Equilibrium constant for the extraction of In by LIX 973N Species
log K ext Žgraphical.
log K ext Žnumerical.
s Žlog K ext .
U
s
InR 3
y7.7
y8.27"0.04
0.01
0.22
0.08
calculations. This stoichiometry agrees well with that reported using Cyanex 301 and LIX 984 extractants w3,6x. Furthermore, various tests were carried out in order to determine the influence of the aqueous ionic media on the extraction of In ŽIII. by LIX 973N at a constant ionic strength of 0.5 M. As seen in Fig. 4, in which the percentage of indium extraction vs. pH eq is represented, the extraction efficiency follows the order nitrate 4 chlorides sulphate. The presence of chloride ions in the aqueous solution do not enhance indium extraction as has been shown earlier w4x; indium ŽIII. forms stable complexes with chloride and sulphate ions which possibly compete with the oxime in the extraction of the metal. On the other hand, the presence of nitrate anion, Žwhich forms only very weak nitrate complexes with indium ŽIII.., in the aqueous solution significantly influences the extraction of indium by LIX 973N with respect to the extraction of the metal from aqueous solutions of near zero ionic strength ŽFig. 4.. This indicates that the presence of this anion in the aqueous solution produces a salting-out effect, which could be tentatively interpreted by the use of activity coefficients and appropriate modelling, e.g., SIT, Davies model, etc.
Fig. 4. Percentage of extraction of indium by LIX 973N from various ionic media as a function of the equilibrium pH. Aqueous phase: 0.1 grl In. Organic phase: 5% vrv LIX 973N in xylene. Temperature 208C. Equilibration time 20 min. OrA ratio 1.
F.J. Alguacilr Hydrometallurgy 51 (1999) 97–102
102
4. Conclusions The results obtained show that the commercially available extractant LIX 973N can be used as a reagent for indium extraction in sulphate media at moderate acidic pH values and low aqueous ionic strength. The extraction reaction is endothermic Ž D H8 s 21.1 kJrmol. and is dependent on the aqueous pH and the extractant concentration. The extraction of indium proceeds by a cation exchange reaction, indium is extracted into the organic phase by the formation of a single species of probable stoichiometry InR 3 with log K ext s y8.27 " 0.04 Žnum... No polynuclear indium complexes are formed in the experimental conditions used. The efficiency of the indium extraction is strongly dependent on the counter-anion Žchloride, sulphate, nitrate. present in the aqueous solution.
Acknowledgements To the CSIC ŽSpain. for support to carry out this work.
References w1x w2x w3x w4x w5x w6x w7x w8x
G.M. Ritcey, A.W. Ashbrook, Solvent Extraction, Part II, Elsevier, Amsterdam Ž1979., p. 556. S. Amer, Rev. Met. 17 Ž2. Ž1981. 109. M. Avila Rodriguez, G. Cote, D. Bauer, Solvent Extr. Ion Exch. 10 Ž5. Ž1992. 811. S. Facon, M. Avila Rodriguez, G. Cote, D. Bauer, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 1, SCI-Elsevier Applied Science, London Ž1993., p. 557. M.A. Karve, S.M. Khopar, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 3, SCI-Elsevier Applied Science, London Ž1993., p. 1347. E. Rodriguez de San Miguel, J.C. Aguilar, J.P. Bernal, M.L. Ballinas, M.T.J. Rodriguez, J. de Gyves, K. Schimmel, Hydrometallurgy 47 Ž1997. 19. Ž1997.. Henkel KGaA, LIX 973N Material Safety Data Sheet, Dusseldorf ¨ D.H. Liem, Acta Chem. Scand. 25 Ž1971. 1521.