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Solvent extraction of molybdenum (VI), tungsten (VI) and rhenium (VII) by diisododecylamine from leach liquors
Hydrometallurgy 60 Ž2001. 1–5 www.elsevier.nlrlocaterhydromet
Solvent extraction of molybdenum žVI/ , tungsten žVI/ and rhenium žVII/ by diisododecylamine from leach liquors N. Iatsenko Gerhardt, A.A. Palant ) , V.A. Petrova, R.K. Tagirov Institute of Metallurgy and Materials, Russian Academy of Sciences, IMET RAN, B-334, Leninsky Prospect 49, Moscow 117911, Russia Received 16 March 1999; received in revised form 2 June 2000; accepted 3 June 2000
Abstract Solvent extraction of molybdenum ŽVI., tungsten ŽVI. and rhenium ŽVII. by diisododecylamine ŽDIDA. from leach liquors encountered in the processing of tungsten and molybdenum ores was studied. This study applies results published previously. Solutions formed during the oxidizing roasting operation of molybdenite sulphide concentrates obtained from a wet dust collector Ž1.15 grL Re and 18.6 grL Mo, 1.1 M H 2 SO4 . and leach liquor formed during the autoclave soda decomposition process of wolframite concentrates were used. The organic phase comprised 15% vrv technical grade DIDA Ž86% DIDA q 14% tri-n-octyl amine ŽTOA.. in ‘light’ kerosene Žboiling point 200–2508C. without modifiers. Recovery of tungsten and molybdenum in organic phase using a second stage extraction scheme was ) 99%, and the recovery of tungsten was 99.9% using the first stage of solvent extraction. However, the formation of stable dispersion was observed during the extraction of tungsten by DIDA from concentrated solutions Ž) 100 grL.. The formation of stable dispersion can be avoided by diluting the solution to 50 grL W ŽVI.. Metals in the loaded organic phase were stripped quantitatively by aqueous ammonium solution at an aqueousrorganic phase ratio ranging from 1:1 to 1:2 in either the first or second stage scheme. The organic phase was regenerated by treatment with 10% H 2 SO4 and was re-used in extraction. We demonstrate that DIDA is an extractant specific enough for rare refractory metals and that the co-extraction of such impurities as copper, magnesium, manganese, iron, aluminum and cobalt does not exceed 1–2%. q 2001 Published by Elsevier Science B.V. Keywords: Molybdenum; Tungsten; Rhenium
1. Introduction Amines are widely used extractants for rare elements w1–7x. In general, the efficiency of metal extraction by amines decreases as follows: quaternary ) tertiary ) secondary ) primary when metal
)
Corresponding author.
ion complexes are extracted under the same conditions. Although certain difficulties are encountered in stripping metals using quaternary ammonium compounds, tertiary amines have found wide application in practical extraction systems. Among these is trin-octyl amine ŽTOA., which extracts metal ion complexes by an anion-exchange reaction w1–7x. Kerosene with added modifiers of the organic phase Žalcohols or ketones. is usually used in diluting TOA.
0304-386Xr01r$ - see front matter q 2001 Published by Elsevier Science B.V. PII: S 0 3 0 4 - 3 8 6 X Ž 0 0 . 0 0 1 2 3 - 7
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
2
Table 1 Correlation of constant extraction values of tungsten ŽVI., molybdenum ŽVI. and rhenium ŽVII. by TOA and DIDA Metal
W Mo Re a
Extraction constant Žlog K . TOAa
DIDAa
2.60 1.50 2.25
3.68 1.80 2.85
Diluent — kerosene, sulphuric acid solution.
Previous work by our group and others w8–11x has shown that the extraction of tungsten, molybdenum and rhenium from acid solutions by a new extractant from the class of secondary amines, diisododecylamine ŽDIDA., is as effective as the widely used extractant TOA ŽTable 1.. The reason for this is that steric and competitive effects of mineral acids manifest themselves less for secondary amines Žthe decreasing number of alkyl radicals attached to nitrogen atom favors the effective extraction of large anions. w1,9,10x. Among the advantages of DIDA over TOA is that it can be used as an extractant without a modifier. Because no modifier is used, DIDA is a feasible alternate extractant to TOA for the extraction of rare refractory metals from the solutions of complex salt composition obtained in industrial processing of tungsten and molybdenum concentrates. This article is devoted to the extraction of W, Mo, and Re by DIDA from leach liquors and the estimation of extractant selectivity for the separation of refractory elements from accompanying impurities.
2. Experimental Technical DIDA consisting of a mixture of 86% pure DIDA Ž) 99%. and 14% TOA was used w8x. The composition of the organic phase is as follows: 15% vrv technical DIDA and 85% vrv AlightB kerosene without organic phase modifiers. Conversion of the amine into sulphate salts was accomplished by treating the amine with 10% sulphuric acid at an aqueousrorganic phase ratio of 1:1. Leach liquor formed during the autoclave soda decomposition process of wolframite concentrates was used w12,13x. The composition of the tungsten
leach liquor is as follows: W ) 120 grL; Mo - 0.1 grL; Si ; 1 grL; As - 0.2 grL; Na 2 CO 3 60 grL. The purification of leach liquor from Si prior to extraction was done by the hydrolytic precipitation of silicic acid at pH 7 w12x, and the subsequent acidification of the solution with sulphuric acid to pH 2. Rhenium- and molybdenum-containing solutions formed during the oxidizing roasting operation of molybdenite sulphide concentrates in a fluidized bed furnace were obtained from a wet dust collector w12,14x. The composition of the solution is given in Table 2. The solution was not processed further before extraction. Selectivity of DIDA for the rare refractory metals was shown by using a molybdenum-containing synthetic sulphuric acid solution in which the salts Al 2 ŽSO4 . 2 , CoSO4 , MnSO4 and MgSO4 Žanalytical reagent grade. were added. The efficiency of metal extraction by DIDA was determined to decrease as follows: W ) Re ) Mo. The composition of the initial synthetic solution was as follows ŽgrL.: Cu 0.95; Mn 2.05; Fe 1.20; Co 1.10; Al 1.42; Mg 0.67; Mo 1.19; H 2 SO4 Ž1.0 M.. Purified Ž) 99%. DIDA obtained by vacuum distillation at 160–1648C and 1 mm Hg of a technical grade solution was used in this study. The separation factor of molybdenum in relation to other metals was taken as the ratio of the corresponding distribution coefficients Ž D Mo rD Re .; the separation efficiency was taken as the ratio of the corresponding extraction percentages Ž E Mo rERe .. Metal concentrations in the aqueous solution were analyzed by either inductively coupled plasma atomic emission spectrometry ŽICP. or a photocolorimetric method. The metal concentration in the organic phase was calculated by mass balance. Phases remained in contact for 5–7 min in the mixture at room temperature w9–11x.
Table 2 Chemical composition of the solution obtained from a wet dust collector during oxidizing roasting of molybdenite sulphide concentrates Chemical composition of the solution ŽgrL. Re
Mo
Fe
Cu
H 2 SO4
1.15
13.6
4.5
1.5
106
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
3. Results and discussion
Table 4 Extraction percentage of rhenium ŽVII. and molybdenum ŽVI. from the solution obtained from the wet dust collector Ž15% vrv DIDA in kerosene at a phase ratio of aqueousrorganic of 1:1.
3.1. Extraction of tungsten by DIDA Preliminary experiments showed that tungsten can be extracted quantitatively by DIDA at a pH of 2. However, the formation of a stable dispersion was observed during the extraction of tungsten by DIDA from concentrated solutions Ž) 100 grL W ŽVI... The stable dispersion did not separate within 7 days. Separation of phases could be achieved within 2–3 min if the tungsten-containing leach liquor was diluted to a tungsten concentration of less than 50 grL. The observed phenomenon does not limit the practical application of DIDA since the dilution of the leach liquor with recycled solutions, neutralization by mineral acids and purification from accompanying impurities results in concentration of less than 50 grL w12,13x. Experimental data given in Table 3 show solvent extraction and stripping of W ŽVI. with aqueous ammonium solution from the diluted leach liquor Ža dilution factor of 4.. As shown in the table, the tungsten recovery by DIDA is ) 99% after the first stage of extraction. The stripping of tungsten with aqueous ammonium solution from the loaded organic solution in the case of DIDA extraction is analogous to systems
Table 3 Extraction of tungsten by 15% vrv DIDA in kerosene from diluted leach liquor at pH 2 Product
Phase ratio Žaqueousr organic.
W ŽVI. ŽgrL.
W ŽVI. extracted Ž%.
Feed solutiona 1st Stage raffinate 2nd Stage raffinate 1st Stripping c Control stripping d
– 1:1 1:1 1:2 1:2
24.0 0.033 0.030 44.8 2.95
– 99.86 99.88 b 93.0 6.2 Ž99.2 e .
a
Diluted leach liquor. The combined extraction percentage for two stages of extraction and stripping. c Aqueous phase after the first stage of stripping Ž15 vol.% NH 4 OH.. d Second stage stripping. e The combined extraction percentage for two stages of extraction and stripping. b
3
Extraction stage
Raffinate content ŽgrL.
Percent extracted
Re
Mo
Re
Mo
0.15 0.01
97.9 99.4 b
99.2 99.9 b
Regenerated organic phase c 1st Stage 0.18 0.22 2nd Stage 0.03 0.03 3rd Stage 0.006 0.01
83.9 97.4 b 99.5 b
98.8 99.8 b 99.9 b
Fresh organic phase a 1st Stage 0.023 2nd Stage 0.07
a
Organic phase consisted of stock chemicals. Combined extraction percentage of metals for two and three stages of extraction. c Organic phase regenerated as described in Section 2. b
based on TOA. Localized crystallization of ammonium paratungstate was observed w13x. The issues associated with preventing the occurrence of this phenomenon in the extraction processing of tungstate solutions are discussed in detail elsewhere w4,5,12,13x. In short, two-stage stripping with aqueous ammonium solution provides high recovery Ž99.2%. of metal in the ammonium solution ŽTable 3.. Ammonium paratungstate was precipitated by evaporation of the ammonium solution containing up to 50 grL W w12x. 3.2. Extraction of rhenium and molybdenum by DIDA Extraction of Mo ŽVI. and Re ŽVII. by DIDA from solutions formed during oxidizing roasting operation of molybdenite sulphide concentrates and obtained from a wet dust collector is presented in Table 4. The recovery of metals in the organic phase in the two stages is ) 99%. Excellent phase separation performance Žrapid phase separation, no formation of the third phase and no generation of an emulsion. in the extraction process was observed. Metals were stripped by ammonia Ž1:1. solution at an aqueousrorganic phase ratio of between 1:1 and 1:2. After the stripping, the organic phase was regenerated by treatment with 10% sulphuric acid and was subsequently used for the extraction of molybdenum and rhenium. As shown in Table 4, the
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
4
Table 5 Extraction of molybdenum ŽVI. by 7% vrv DIDA in kerosene in the presence of potential contaminating metalsa Metal
Feed solution content ŽgrL.
Metal in raffinate ŽgrL.
Extraction percentage
Separation factor b
Separation efficiency b
Mo Cu Mn Fe Co Al Mg
1.92 0.95 2.05 1.20 1.10 1.42 0.67
0.092 0.95 2.05 1.15 1.05 1.40 0.66
95.2 - 0.01 - 0.1 2.1 2.2 0.35 0.75
– ) 3000 ) 3000 933 853 1806 2650
– ) 1000 ) 1000 45.3 45.3 272 127
a b
Phase ratio aqueousrorganics 1:1, 1st stage of extraction. Factors and efficiencies reported in terms of MorMe.
decrease in efficiency of metal extraction using the regenerated organic phase was slight. The secondary amine DIDA is, thus, an effective and practical extractant for extraction of tungsten, molybdenum and rhenium from acid solutions.
Ž2. The selectivity of DIDA for refractory metals was estimated and the co-extraction of copper, magnesium, manganese, iron, cobalt, and aluminum was found not to exceed 1–2%.
3.3. SelectiÕity of DIDA
References
The selectivity of molybdenum extraction by DIDA from solutions containing copper, magnesium, manganese, iron, cobalt and aluminum is presented in Table 5. The co-extraction of iron, cobalt and magnesium impurities does not exceed 1–2%. Copper, manganese and aluminum are co-extracted at values at 0.5% or less. For all practical purpose, these metals are not extracted into the organic phase. Consequently, DIDA, like TOA w12,14x is selective enough for refractory metals, and it is possible to separate these metals from other potential cationic impurities.
4. Conclusions Ž1. Solvent extraction of molybdenum ŽVI., tungsten ŽVI. and rhenium ŽVII. by DIDA from leach liquors mentioned in the processing of tungsten and molybdenum ores was studied. Under optimal conditions, the extraction percentage of these metals in the organic phase was found to be more than 99% during the first two stages of the extraction under optimal conditions. The metals in the loaded organic phase were stripped quantitatively with aqueous ammonia solution.
w1x B.S. Shmidt, Extraction by Amines, Atomizdat, Moscow, 1970, 312 pp. Žin Russian.. w2x A.N. Zelikman, L. Dregan, The extraction of rhenium from sulphuric solutions by organic solvents, J. Inorg. Chem. 12 Ž1. Ž1967. 261–268 Žin Russian.. w3x C.K. Vun, A mathematical description of the extraction isotherms of tungsten and sulphuric acid in a tertiary amine, Hydrometallurgy 12 Ž3. Ž1984. 285–295. w4x J. Coca, F.V. Duez, M.A. Moris, Solvent extraction of molybdenum and tungsten by Alamine 336 and DEHPA, Hydrometallurgy 25 Ž2. Ž1990. 125–133. w5x R.A. De Carvalho Cruedes, M.N.M. Sampaio, Solvent extraction of tungsten by alkylamines — hydrochloric acid and alkylamines–sulphuric acid systems, Hydrometallurgy 26 Ž2. Ž1991. 137–142. w6x S.I. Stepanov, Chemistry of solvent extraction of rare metals by quaternary ammonium salts, ISEC ’96, Melbourne, 19–23 March, 1996 1 Ž1996. 553–558, Melbourne. w7x E.G. Tarasova, M.M. Bogomolova, Study of sorption and solvent extraction of molybdenum from sulphuric acid solution by anion exchanger AB-17 and TAA using the IR-spectroscopy method, Complexnoe Ispolzovanie Mineral. Syrya 3 Ž1992. 58–62 Žin Russian.. w8x N.G. Zhukova, L.I. Sokolskay, Anion-exchange extractants with controllable selectivity, Tsvetn. Metall. 3 Ž1991. 47–48, Žin Russian.. w9x A.A. Palant, V.A. Petrova, N.A. Iatsenko, Solvent extraction of tungsten by diisododecylamine from sulphuric acid solution, Met. Bull. AS 3 Ž1998. 23–26. w10x A.A. Palant, V.A. Petrova, N.A. Iatsenko, Solvent extraction of rhenium ŽVII. by diisododecylamine from sulphuric acid solution, J. Inorg. Chem. 43 Ž2. Ž1998. 339–343.
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5 w11x A.A. Palant, N.A. Iatsenko, V.A. Petrova, Solvent extraction of molybdenum ŽVI. by diisododecylamine from sulphuric acid solution, Hydrometallurgy 48 Ž1. Ž1998. 83–90. w12x A.N. Zelikman, Metallurgy of rare refractory metals, Metallurg ŽMoscow. Ž1986. 440 pp.
5
w13x G.P. Giganov, A.M. Tserekova, T.Sh. Agnokov, Extraction technology of oxide tungsten recovery, Tsvetn. Metall. 5 Ž1998. 67–71 Žin Russian.. w14x A.K. Kobzhasov, A.A. Palant, Metallurgy of rhenium, AlmaAt. Ž1992. 161 pp.
Solvent extraction of molybdenum žVI/ , tungsten žVI/ and rhenium žVII/ by diisododecylamine from leach liquors N. Iatsenko Gerhardt, A.A. Palant ) , V.A. Petrova, R.K. Tagirov Institute of Metallurgy and Materials, Russian Academy of Sciences, IMET RAN, B-334, Leninsky Prospect 49, Moscow 117911, Russia Received 16 March 1999; received in revised form 2 June 2000; accepted 3 June 2000
Abstract Solvent extraction of molybdenum ŽVI., tungsten ŽVI. and rhenium ŽVII. by diisododecylamine ŽDIDA. from leach liquors encountered in the processing of tungsten and molybdenum ores was studied. This study applies results published previously. Solutions formed during the oxidizing roasting operation of molybdenite sulphide concentrates obtained from a wet dust collector Ž1.15 grL Re and 18.6 grL Mo, 1.1 M H 2 SO4 . and leach liquor formed during the autoclave soda decomposition process of wolframite concentrates were used. The organic phase comprised 15% vrv technical grade DIDA Ž86% DIDA q 14% tri-n-octyl amine ŽTOA.. in ‘light’ kerosene Žboiling point 200–2508C. without modifiers. Recovery of tungsten and molybdenum in organic phase using a second stage extraction scheme was ) 99%, and the recovery of tungsten was 99.9% using the first stage of solvent extraction. However, the formation of stable dispersion was observed during the extraction of tungsten by DIDA from concentrated solutions Ž) 100 grL.. The formation of stable dispersion can be avoided by diluting the solution to 50 grL W ŽVI.. Metals in the loaded organic phase were stripped quantitatively by aqueous ammonium solution at an aqueousrorganic phase ratio ranging from 1:1 to 1:2 in either the first or second stage scheme. The organic phase was regenerated by treatment with 10% H 2 SO4 and was re-used in extraction. We demonstrate that DIDA is an extractant specific enough for rare refractory metals and that the co-extraction of such impurities as copper, magnesium, manganese, iron, aluminum and cobalt does not exceed 1–2%. q 2001 Published by Elsevier Science B.V. Keywords: Molybdenum; Tungsten; Rhenium
1. Introduction Amines are widely used extractants for rare elements w1–7x. In general, the efficiency of metal extraction by amines decreases as follows: quaternary ) tertiary ) secondary ) primary when metal
)
Corresponding author.
ion complexes are extracted under the same conditions. Although certain difficulties are encountered in stripping metals using quaternary ammonium compounds, tertiary amines have found wide application in practical extraction systems. Among these is trin-octyl amine ŽTOA., which extracts metal ion complexes by an anion-exchange reaction w1–7x. Kerosene with added modifiers of the organic phase Žalcohols or ketones. is usually used in diluting TOA.
0304-386Xr01r$ - see front matter q 2001 Published by Elsevier Science B.V. PII: S 0 3 0 4 - 3 8 6 X Ž 0 0 . 0 0 1 2 3 - 7
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
2
Table 1 Correlation of constant extraction values of tungsten ŽVI., molybdenum ŽVI. and rhenium ŽVII. by TOA and DIDA Metal
W Mo Re a
Extraction constant Žlog K . TOAa
DIDAa
2.60 1.50 2.25
3.68 1.80 2.85
Diluent — kerosene, sulphuric acid solution.
Previous work by our group and others w8–11x has shown that the extraction of tungsten, molybdenum and rhenium from acid solutions by a new extractant from the class of secondary amines, diisododecylamine ŽDIDA., is as effective as the widely used extractant TOA ŽTable 1.. The reason for this is that steric and competitive effects of mineral acids manifest themselves less for secondary amines Žthe decreasing number of alkyl radicals attached to nitrogen atom favors the effective extraction of large anions. w1,9,10x. Among the advantages of DIDA over TOA is that it can be used as an extractant without a modifier. Because no modifier is used, DIDA is a feasible alternate extractant to TOA for the extraction of rare refractory metals from the solutions of complex salt composition obtained in industrial processing of tungsten and molybdenum concentrates. This article is devoted to the extraction of W, Mo, and Re by DIDA from leach liquors and the estimation of extractant selectivity for the separation of refractory elements from accompanying impurities.
2. Experimental Technical DIDA consisting of a mixture of 86% pure DIDA Ž) 99%. and 14% TOA was used w8x. The composition of the organic phase is as follows: 15% vrv technical DIDA and 85% vrv AlightB kerosene without organic phase modifiers. Conversion of the amine into sulphate salts was accomplished by treating the amine with 10% sulphuric acid at an aqueousrorganic phase ratio of 1:1. Leach liquor formed during the autoclave soda decomposition process of wolframite concentrates was used w12,13x. The composition of the tungsten
leach liquor is as follows: W ) 120 grL; Mo - 0.1 grL; Si ; 1 grL; As - 0.2 grL; Na 2 CO 3 60 grL. The purification of leach liquor from Si prior to extraction was done by the hydrolytic precipitation of silicic acid at pH 7 w12x, and the subsequent acidification of the solution with sulphuric acid to pH 2. Rhenium- and molybdenum-containing solutions formed during the oxidizing roasting operation of molybdenite sulphide concentrates in a fluidized bed furnace were obtained from a wet dust collector w12,14x. The composition of the solution is given in Table 2. The solution was not processed further before extraction. Selectivity of DIDA for the rare refractory metals was shown by using a molybdenum-containing synthetic sulphuric acid solution in which the salts Al 2 ŽSO4 . 2 , CoSO4 , MnSO4 and MgSO4 Žanalytical reagent grade. were added. The efficiency of metal extraction by DIDA was determined to decrease as follows: W ) Re ) Mo. The composition of the initial synthetic solution was as follows ŽgrL.: Cu 0.95; Mn 2.05; Fe 1.20; Co 1.10; Al 1.42; Mg 0.67; Mo 1.19; H 2 SO4 Ž1.0 M.. Purified Ž) 99%. DIDA obtained by vacuum distillation at 160–1648C and 1 mm Hg of a technical grade solution was used in this study. The separation factor of molybdenum in relation to other metals was taken as the ratio of the corresponding distribution coefficients Ž D Mo rD Re .; the separation efficiency was taken as the ratio of the corresponding extraction percentages Ž E Mo rERe .. Metal concentrations in the aqueous solution were analyzed by either inductively coupled plasma atomic emission spectrometry ŽICP. or a photocolorimetric method. The metal concentration in the organic phase was calculated by mass balance. Phases remained in contact for 5–7 min in the mixture at room temperature w9–11x.
Table 2 Chemical composition of the solution obtained from a wet dust collector during oxidizing roasting of molybdenite sulphide concentrates Chemical composition of the solution ŽgrL. Re
Mo
Fe
Cu
H 2 SO4
1.15
13.6
4.5
1.5
106
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
3. Results and discussion
Table 4 Extraction percentage of rhenium ŽVII. and molybdenum ŽVI. from the solution obtained from the wet dust collector Ž15% vrv DIDA in kerosene at a phase ratio of aqueousrorganic of 1:1.
3.1. Extraction of tungsten by DIDA Preliminary experiments showed that tungsten can be extracted quantitatively by DIDA at a pH of 2. However, the formation of a stable dispersion was observed during the extraction of tungsten by DIDA from concentrated solutions Ž) 100 grL W ŽVI... The stable dispersion did not separate within 7 days. Separation of phases could be achieved within 2–3 min if the tungsten-containing leach liquor was diluted to a tungsten concentration of less than 50 grL. The observed phenomenon does not limit the practical application of DIDA since the dilution of the leach liquor with recycled solutions, neutralization by mineral acids and purification from accompanying impurities results in concentration of less than 50 grL w12,13x. Experimental data given in Table 3 show solvent extraction and stripping of W ŽVI. with aqueous ammonium solution from the diluted leach liquor Ža dilution factor of 4.. As shown in the table, the tungsten recovery by DIDA is ) 99% after the first stage of extraction. The stripping of tungsten with aqueous ammonium solution from the loaded organic solution in the case of DIDA extraction is analogous to systems
Table 3 Extraction of tungsten by 15% vrv DIDA in kerosene from diluted leach liquor at pH 2 Product
Phase ratio Žaqueousr organic.
W ŽVI. ŽgrL.
W ŽVI. extracted Ž%.
Feed solutiona 1st Stage raffinate 2nd Stage raffinate 1st Stripping c Control stripping d
– 1:1 1:1 1:2 1:2
24.0 0.033 0.030 44.8 2.95
– 99.86 99.88 b 93.0 6.2 Ž99.2 e .
a
Diluted leach liquor. The combined extraction percentage for two stages of extraction and stripping. c Aqueous phase after the first stage of stripping Ž15 vol.% NH 4 OH.. d Second stage stripping. e The combined extraction percentage for two stages of extraction and stripping. b
3
Extraction stage
Raffinate content ŽgrL.
Percent extracted
Re
Mo
Re
Mo
0.15 0.01
97.9 99.4 b
99.2 99.9 b
Regenerated organic phase c 1st Stage 0.18 0.22 2nd Stage 0.03 0.03 3rd Stage 0.006 0.01
83.9 97.4 b 99.5 b
98.8 99.8 b 99.9 b
Fresh organic phase a 1st Stage 0.023 2nd Stage 0.07
a
Organic phase consisted of stock chemicals. Combined extraction percentage of metals for two and three stages of extraction. c Organic phase regenerated as described in Section 2. b
based on TOA. Localized crystallization of ammonium paratungstate was observed w13x. The issues associated with preventing the occurrence of this phenomenon in the extraction processing of tungstate solutions are discussed in detail elsewhere w4,5,12,13x. In short, two-stage stripping with aqueous ammonium solution provides high recovery Ž99.2%. of metal in the ammonium solution ŽTable 3.. Ammonium paratungstate was precipitated by evaporation of the ammonium solution containing up to 50 grL W w12x. 3.2. Extraction of rhenium and molybdenum by DIDA Extraction of Mo ŽVI. and Re ŽVII. by DIDA from solutions formed during oxidizing roasting operation of molybdenite sulphide concentrates and obtained from a wet dust collector is presented in Table 4. The recovery of metals in the organic phase in the two stages is ) 99%. Excellent phase separation performance Žrapid phase separation, no formation of the third phase and no generation of an emulsion. in the extraction process was observed. Metals were stripped by ammonia Ž1:1. solution at an aqueousrorganic phase ratio of between 1:1 and 1:2. After the stripping, the organic phase was regenerated by treatment with 10% sulphuric acid and was subsequently used for the extraction of molybdenum and rhenium. As shown in Table 4, the
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5
4
Table 5 Extraction of molybdenum ŽVI. by 7% vrv DIDA in kerosene in the presence of potential contaminating metalsa Metal
Feed solution content ŽgrL.
Metal in raffinate ŽgrL.
Extraction percentage
Separation factor b
Separation efficiency b
Mo Cu Mn Fe Co Al Mg
1.92 0.95 2.05 1.20 1.10 1.42 0.67
0.092 0.95 2.05 1.15 1.05 1.40 0.66
95.2 - 0.01 - 0.1 2.1 2.2 0.35 0.75
– ) 3000 ) 3000 933 853 1806 2650
– ) 1000 ) 1000 45.3 45.3 272 127
a b
Phase ratio aqueousrorganics 1:1, 1st stage of extraction. Factors and efficiencies reported in terms of MorMe.
decrease in efficiency of metal extraction using the regenerated organic phase was slight. The secondary amine DIDA is, thus, an effective and practical extractant for extraction of tungsten, molybdenum and rhenium from acid solutions.
Ž2. The selectivity of DIDA for refractory metals was estimated and the co-extraction of copper, magnesium, manganese, iron, cobalt, and aluminum was found not to exceed 1–2%.
3.3. SelectiÕity of DIDA
References
The selectivity of molybdenum extraction by DIDA from solutions containing copper, magnesium, manganese, iron, cobalt and aluminum is presented in Table 5. The co-extraction of iron, cobalt and magnesium impurities does not exceed 1–2%. Copper, manganese and aluminum are co-extracted at values at 0.5% or less. For all practical purpose, these metals are not extracted into the organic phase. Consequently, DIDA, like TOA w12,14x is selective enough for refractory metals, and it is possible to separate these metals from other potential cationic impurities.
4. Conclusions Ž1. Solvent extraction of molybdenum ŽVI., tungsten ŽVI. and rhenium ŽVII. by DIDA from leach liquors mentioned in the processing of tungsten and molybdenum ores was studied. Under optimal conditions, the extraction percentage of these metals in the organic phase was found to be more than 99% during the first two stages of the extraction under optimal conditions. The metals in the loaded organic phase were stripped quantitatively with aqueous ammonia solution.
w1x B.S. Shmidt, Extraction by Amines, Atomizdat, Moscow, 1970, 312 pp. Žin Russian.. w2x A.N. Zelikman, L. Dregan, The extraction of rhenium from sulphuric solutions by organic solvents, J. Inorg. Chem. 12 Ž1. Ž1967. 261–268 Žin Russian.. w3x C.K. Vun, A mathematical description of the extraction isotherms of tungsten and sulphuric acid in a tertiary amine, Hydrometallurgy 12 Ž3. Ž1984. 285–295. w4x J. Coca, F.V. Duez, M.A. Moris, Solvent extraction of molybdenum and tungsten by Alamine 336 and DEHPA, Hydrometallurgy 25 Ž2. Ž1990. 125–133. w5x R.A. De Carvalho Cruedes, M.N.M. Sampaio, Solvent extraction of tungsten by alkylamines — hydrochloric acid and alkylamines–sulphuric acid systems, Hydrometallurgy 26 Ž2. Ž1991. 137–142. w6x S.I. Stepanov, Chemistry of solvent extraction of rare metals by quaternary ammonium salts, ISEC ’96, Melbourne, 19–23 March, 1996 1 Ž1996. 553–558, Melbourne. w7x E.G. Tarasova, M.M. Bogomolova, Study of sorption and solvent extraction of molybdenum from sulphuric acid solution by anion exchanger AB-17 and TAA using the IR-spectroscopy method, Complexnoe Ispolzovanie Mineral. Syrya 3 Ž1992. 58–62 Žin Russian.. w8x N.G. Zhukova, L.I. Sokolskay, Anion-exchange extractants with controllable selectivity, Tsvetn. Metall. 3 Ž1991. 47–48, Žin Russian.. w9x A.A. Palant, V.A. Petrova, N.A. Iatsenko, Solvent extraction of tungsten by diisododecylamine from sulphuric acid solution, Met. Bull. AS 3 Ž1998. 23–26. w10x A.A. Palant, V.A. Petrova, N.A. Iatsenko, Solvent extraction of rhenium ŽVII. by diisododecylamine from sulphuric acid solution, J. Inorg. Chem. 43 Ž2. Ž1998. 339–343.
N.I. Gerhardt et al.r Hydrometallurgy 60 (2001) 1–5 w11x A.A. Palant, N.A. Iatsenko, V.A. Petrova, Solvent extraction of molybdenum ŽVI. by diisododecylamine from sulphuric acid solution, Hydrometallurgy 48 Ž1. Ž1998. 83–90. w12x A.N. Zelikman, Metallurgy of rare refractory metals, Metallurg ŽMoscow. Ž1986. 440 pp.
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w13x G.P. Giganov, A.M. Tserekova, T.Sh. Agnokov, Extraction technology of oxide tungsten recovery, Tsvetn. Metall. 5 Ž1998. 67–71 Žin Russian.. w14x A.K. Kobzhasov, A.A. Palant, Metallurgy of rhenium, AlmaAt. Ž1992. 161 pp.