- Email: [email protected]
Solvent extraction equilibria in the CuSO4H2SO4H2OLIX 860-kerosene system
Minerals Engineering, Vol. 11, No. 9, pp. 821-826, 1998
Pergamon 0892-6875(98)00069-7
SOLVENT EXTRACTION EQUILIBRIA CuSO4-H2SO4-H20-LIX 860-KEROSENE
© 1998 Published by Elsevier Science Ltd All rights reserved 0892-6875/98/$ - - see front matter
IN THE SYSTEM
D. D O U N G D E E T H A V E E R A T A N A and H.Y. S O H N Departments of Metallurgical Engineering and of Chemical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112-0114, USA. E-mail: [email protected] (Received 13 April 1998; accepted 22 June 1998)
ABSTRACT The equilibrium isotherm and distribution coefficients were determined for the CuSO4--H2SO4-H20-LIX 860-kerosene solvent extraction system at 25°C and aqueous copper concentrations below 500 mg/L. A previously developed thermodynamic model for extraction equilibria closely predicted the experimentally measured distribution coefficients. © 1998 Published by Elsevier Science Ltd. All rights reserved
Keywords Hydrometallurgy; solvent extraction; extractive metallurgy
INTRODUCTION The equilibrium reaction for the liquid-liquid extraction of the divalent cupric ion has been studied by several investigators [1-5]. Russell and Rickel [2] modeled Cu extraction from acidic sulfate solutions using commercial extractants 5-nonylsalicylaldoxime with nonylphenol modifier (P5100), 5-nonylsalicylaldoxime with tridecanol modifier (PT5050), and 2-hydroxy-5-nonylacetophenone oxime (LIX 84). The mathematical model consisting of sets of mass action and mass balance equations was solved for equilibrium extraction constants. Hoh and Bautista [3] investigated a thermodynamic equilibrium model to predict distribution coefficients in the Cu-LIX 65N and Cu-Kelex 100 systems. Lee et al. [4] developed an equilibrium model and applied it to the distribution coefficients and the equilibrium extraction constants of zinc in the ZnSO4-H2SO4-H20-D2EHPA-kerosene system, copper in the CuSO4-H2SO4-H20-LIX 65N-toluene system, and nickel in the NiSO4-CH3COOH-NaOH-Kelex 100-xylene system. The model was developed using the K-value method for the solvent extraction of divalent metal ions from sulfuric acid solutions. It calculates the chemical species concentrations and activity coefficients from experimental data and predicts the distribution coefficients of metal from initial extraction conditions. Yoshizuka et al. [5] presented equilibrium studies on the solvent extraction of copper (II) with 5-dodecylsalicylaldoxime. It was indicated that copper (II) was extracted as a chelate of the type CuA 2 in the organic solution. In this work, the extraction equilibria of the extraction of copper from sulfate solutions by LIX 860 in kerosene were studied, and the mathematical model developed by Lee et al. [4] was used to predict the distribution coefficients and the equilibrium extraction constant. The experimental data were compared with the predicted values. The extraction reaction in this system can be expressed as (Cu2+)aq + (2 HA)org = (CuA2)org + (2H+)aq
821
822
D. Doungdeethaveeratanaand H. Y. Sohn EXPERIMENTAL WORK
The extractant used in this work was LIX 860 (average MW = 306), which is a mixture of water-insoluble 5-dodecylsalicylaldoxime (MW = 308) in 2-hydroxy-5-nonylacetophenone oxime (MW = 277) and a highflashpoint kerosene. This copper extractant was obtained from Henkel Corp. and used as received without further purification. Kerosene of commercial reagent grade was used as the diluent also without further purification. The working organic phase was prepared by dissolving LIX 860 in the diluent. The content of LIX 860 in the mixture was 2 vol. %. The aqueous copper solution was prepared by dissolving copper (II) sulfate of AR grade in water. The pH of the aqueous solution was controlled by adding sulfuric acid. The equilibrium isotherm for extraction was obtained by contacting the aqueous (500 mg Cu/L) and organic solutions to equilibrium at various O/A ratios, namely 10:1, 5:1, 3:1, 2:1, 1:1, 1:2, 1:5, and 1:10. The contacting was achieved by vigorous mixing using a magnetic stirrer. Contacting for 15 minutes for the ratios between 2:1 and 1:2 and for 30 minutes for other ratios was found sufficient to attain equilibrium. To ascertain that the true equilibrium isotherm was obtained, equilibrium was also approached starting with an organic phase containing some copper. This was done by first dissolving the predetermined amount of copper sulfate in a small volume of water and contacting this solution with the organic phase for 10 minutes, after which water was added to the aqueous phase to the same total volume as before. The two phases were then allowed to reach equilibrium. The concentration of copper in the aqueous phase was measured by using direct current plasma emission spectrometry (DCP). The instrument was a Beckman l spectrometer, model Spectraspan V, which has a SpectraJet III direct current plasma as the energy source and a high performance echelle grating monochromator. The concentration of the metal in the organic phase was calculated from the mass balance. The pH of the aqueous phase was measured by a pH meter (Orion pH meter model 720A). RESULTS AND DISCUSSION Experiments were carried out at different initial pH values, room temperature, and a fixed initial concentration of the extractant in organic solvent. For the overall extraction equation given by equation 1, the equilibrium constant can be expressed by: K
: ex
(CuA2)°~g(H')2"q Y C u , ~ '
(1)
( C u 2')aq(HA)2org Tcu ~"~HA
The distribution coefficient of metal is defined as:
DM: (M)°rg ,t°tal
(2)
(M)aq,total
A mathematical model of extraction equilibrium using the K-value method developed by Lee et al. [4] was used to analyze the experimental results. The equilibrium data obtained in this work and calculated following the procedure described by Lee et al. [4] are given in Table 1. The equilibrium constant of the overall copper extraction, Kex, was calculated to be 297 ± 5. The experimental and calculated values of the distribution coefficient are plotted in Figure 1. Good agreement between the calculated and experimental data is indicated by the standard deviation value of 0.139 between these two results.
tBeckman SpectramctdcsInc., Andover,Massachusetts
Solvent extraction equilibria TABLE 1
823
Experimental and calculated equilibrium data for the extraction of copper in the C n S O 4 - H 2 S O 4 - I t 2 0 - L I X 860-kerosene system. (Extractant concentration = 0.036
mol/L.) Experimental Conditions
No.
I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
(pI'I)i,~a
1.84 1.90 2.06
(C u)i,al----~ (Cu),q,t,~ mol/L mol/L 0.008 0.007
2.07 2.09 2.27 2.29 2.35
2.99 3.22 4.12
0.008 0.004 0.007 0.008 0.008 0.012 0.017 0.018 0.019 0.020 0.021 0.022 0.023 0.008
K~
Log(Du.~, ) Log('Du.,~)
1.51 × 10-4 1.75 × 10-4 1.46 × 10-4
302 297 297
1.69 1.63 1.84
1.55 1.64 1.90
1.06 × 10-4 1.04 × 10-4 1.06 × 10-4 1.00 X 10-4 3 . 9 0 x 10-s 1.31 × 10-4 1.60x 10.5 3.00 × 10-5 4.50 × 10.5 4.60 × 10"s 1.60 × 10.4 7.90 × 10-4 2.36x10- 3 2.15 x 10.3 3.93 X 10.3 4.72 X 10.3 5.51 × 10.3 6.30 × 10-3 2.60 x 105 2.90 x 10"s 1.80 x 10s 3.70 x 10"s
297 297 297 297 297 297 296 297 296 297 295 296 298 297 299 298 297 297 297 297 297 297
1.84 1.85 1.84 1.87 2.31 1.76 2.36 2.38 2.24 2.22 1.87 1.30 0.83 0.71 0.61 0.53 0.47 0.41 2.46 2.42 2.61 2.32
1.90 1.90 1.90 1.90 2.04 2.10 2.52 2.24 2.12 2.14 1.99 1.08 0.97 0.69 0.52 0.42 0.64 0.52 2.47 2.49 2.57 2.55
Design of a continuous extraction process requires information on equilibrium isotherm. The extraction of copper is usually carried out in the pH range from 1 to 3 in commercial processes [6, 7]. In this study, an equilibrium isotherm was determined at a starting pH of 2.1 _+0.1. The concentration of the aqueous phase used in this study was low (in the range of 470 _+ 30 mg/L) because this study was concerned mainly with application to the treatment of low-concentration copper solutions. As a consequence the pH of the aqueous solution changed by less than 0.2 during extraction. The extraction isotherm data for CuSO4-H2SO4-H20--LIX 860--kerosene system obtained from the phase ratio variation method are shown in Table 2. Equilibrium was reached using a fresh organic solution as well as an organic solution initially containing copper to ascertain that true equilibrium was attained. The same equilibrium state was reached within ten minutes for every phase ratio.
824
D. Doungdeethaveemtana and H. Y. Sohn
0 0
0
u
o
!
2 Log(DM,exp)
Fig. 1
Comparison between calculated and experimental distribution coefficients for Cu extraction with LIX 860.
TABLE 2
Extraction isotherm data. (Initial concentration of Cu in aqueous solution = 492 mg/L Cu. Organic solution = 0.036 M LIX 860 in kerosene)
O/A Ratio
2/1 1/1 2/3 1/2 1/5 1/10
pH
Aqueous, mg/L Cu
Organic, mg/L Cu
1.95 2.06 1.95 2.01 1.95 2.08 2.10 2.17 2.23 2.35 2.34 2.48
1.83 1.44 2.92 2.94 9.64 10.3 38.5 40.5 284 287 390 390
245 245 489 489 724 723 907 903 1040 1020 1020 1020
Solvent extraction equilibria
825
Figure 2 represents the extraction isotherm for copper extraction with 0.036 M LIX 860 in kerosene. The equilibrium isotherm curve can be mathematically represented by the following equation: e
Co,g = e
C,q 3.4145x103, 9.3178x104C~
(mg/L)
(3)
The results of this work indicate that the K-value method of Lee et al. [4] can adequately describe the extraction equilibria in the CuSO4-H2SO4-H20-LIX 860-kerosene system, and that LIX 860 is a strong copper extractant based on the fact that the organic phase becomes saturated at relatively low copper concentration, as can be seen in Figure 2. 10(300'
11300'
r dII o
t
100 ¸
10 .1
1
I0
100
1000
Aq. Phase Cone., mg Cu/L
Fig.2
Equilibrium isotherm for copper extraction with LIX 860 in kerosene (pH = 2.1 _+0.1, temperature = 25°C).
CONCLUSIONS The compound LIX 860 is a strong copper extractant, for which the equilibrium constant of copper extraction, Kex, was determined to be 297_+5. The solvent extraction isotherm for the CuSO4-H2SO4-H20-LIX 860-kerosene system was obtained at 25°C and aqueous copper concentration below 500 mg/L. A previously developed thermodynamic model [4] closely predicted the experimentally measured distribution coefficients.
ACKNOWLEDGMENTS The authors wish to thank the Henkel Corp. for providing the extractant. DD received financial support from the Royal Thai Government during the course of this work. This work was also supported in part by the University of Utah Research Committee and the State of Utah Leasing Fund.
826
D. Doungdeethaveeratanaand H. Y. Sohn REFERENCES
1. .
3. 4. 5. 6. .
Sawistowski, H., in Mass Transfer with Chemical Reaction in Multiphase System, Vol, 1, pp. 667-676, Chemical Publishing Co., New York (1984). Russell, J.H. & Rickel, R.L., Solvent Extraction and Ion Exchange, 8, 855 (1990). Hoh, Y. & Bautista, R.G., Metall. Trans. B, 9B, 69 (1978). Lee, M.S., Lee, E.C. & Sohn, H.Y., J. Chem. Eng. Japan, 29, 781 (1996). Yoshizuka, K., Arita, H., Baba, Y. & Inoue, K., Hydrometallurgy, 23, 247 (1990). Lo, T.C., Baird, M.H.I. & Hanson, C., Handbook of Solvent Extraction, 131,235, 649, WileyInterscience, New York (1983). Kordosky, G.A., The Chemistry of Metals Recovery Using LIX® Reagents, Henkel Corporation, Tucson, Arizona (1990).
Correspondence on papers published in Minerals Engineering is invited, preferably by email to [email protected], or by Fax to +44-(0)1326-318352
Pergamon 0892-6875(98)00069-7
SOLVENT EXTRACTION EQUILIBRIA CuSO4-H2SO4-H20-LIX 860-KEROSENE
© 1998 Published by Elsevier Science Ltd All rights reserved 0892-6875/98/$ - - see front matter
IN THE SYSTEM
D. D O U N G D E E T H A V E E R A T A N A and H.Y. S O H N Departments of Metallurgical Engineering and of Chemical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112-0114, USA. E-mail: [email protected] (Received 13 April 1998; accepted 22 June 1998)
ABSTRACT The equilibrium isotherm and distribution coefficients were determined for the CuSO4--H2SO4-H20-LIX 860-kerosene solvent extraction system at 25°C and aqueous copper concentrations below 500 mg/L. A previously developed thermodynamic model for extraction equilibria closely predicted the experimentally measured distribution coefficients. © 1998 Published by Elsevier Science Ltd. All rights reserved
Keywords Hydrometallurgy; solvent extraction; extractive metallurgy
INTRODUCTION The equilibrium reaction for the liquid-liquid extraction of the divalent cupric ion has been studied by several investigators [1-5]. Russell and Rickel [2] modeled Cu extraction from acidic sulfate solutions using commercial extractants 5-nonylsalicylaldoxime with nonylphenol modifier (P5100), 5-nonylsalicylaldoxime with tridecanol modifier (PT5050), and 2-hydroxy-5-nonylacetophenone oxime (LIX 84). The mathematical model consisting of sets of mass action and mass balance equations was solved for equilibrium extraction constants. Hoh and Bautista [3] investigated a thermodynamic equilibrium model to predict distribution coefficients in the Cu-LIX 65N and Cu-Kelex 100 systems. Lee et al. [4] developed an equilibrium model and applied it to the distribution coefficients and the equilibrium extraction constants of zinc in the ZnSO4-H2SO4-H20-D2EHPA-kerosene system, copper in the CuSO4-H2SO4-H20-LIX 65N-toluene system, and nickel in the NiSO4-CH3COOH-NaOH-Kelex 100-xylene system. The model was developed using the K-value method for the solvent extraction of divalent metal ions from sulfuric acid solutions. It calculates the chemical species concentrations and activity coefficients from experimental data and predicts the distribution coefficients of metal from initial extraction conditions. Yoshizuka et al. [5] presented equilibrium studies on the solvent extraction of copper (II) with 5-dodecylsalicylaldoxime. It was indicated that copper (II) was extracted as a chelate of the type CuA 2 in the organic solution. In this work, the extraction equilibria of the extraction of copper from sulfate solutions by LIX 860 in kerosene were studied, and the mathematical model developed by Lee et al. [4] was used to predict the distribution coefficients and the equilibrium extraction constant. The experimental data were compared with the predicted values. The extraction reaction in this system can be expressed as (Cu2+)aq + (2 HA)org = (CuA2)org + (2H+)aq
821
822
D. Doungdeethaveeratanaand H. Y. Sohn EXPERIMENTAL WORK
The extractant used in this work was LIX 860 (average MW = 306), which is a mixture of water-insoluble 5-dodecylsalicylaldoxime (MW = 308) in 2-hydroxy-5-nonylacetophenone oxime (MW = 277) and a highflashpoint kerosene. This copper extractant was obtained from Henkel Corp. and used as received without further purification. Kerosene of commercial reagent grade was used as the diluent also without further purification. The working organic phase was prepared by dissolving LIX 860 in the diluent. The content of LIX 860 in the mixture was 2 vol. %. The aqueous copper solution was prepared by dissolving copper (II) sulfate of AR grade in water. The pH of the aqueous solution was controlled by adding sulfuric acid. The equilibrium isotherm for extraction was obtained by contacting the aqueous (500 mg Cu/L) and organic solutions to equilibrium at various O/A ratios, namely 10:1, 5:1, 3:1, 2:1, 1:1, 1:2, 1:5, and 1:10. The contacting was achieved by vigorous mixing using a magnetic stirrer. Contacting for 15 minutes for the ratios between 2:1 and 1:2 and for 30 minutes for other ratios was found sufficient to attain equilibrium. To ascertain that the true equilibrium isotherm was obtained, equilibrium was also approached starting with an organic phase containing some copper. This was done by first dissolving the predetermined amount of copper sulfate in a small volume of water and contacting this solution with the organic phase for 10 minutes, after which water was added to the aqueous phase to the same total volume as before. The two phases were then allowed to reach equilibrium. The concentration of copper in the aqueous phase was measured by using direct current plasma emission spectrometry (DCP). The instrument was a Beckman l spectrometer, model Spectraspan V, which has a SpectraJet III direct current plasma as the energy source and a high performance echelle grating monochromator. The concentration of the metal in the organic phase was calculated from the mass balance. The pH of the aqueous phase was measured by a pH meter (Orion pH meter model 720A). RESULTS AND DISCUSSION Experiments were carried out at different initial pH values, room temperature, and a fixed initial concentration of the extractant in organic solvent. For the overall extraction equation given by equation 1, the equilibrium constant can be expressed by: K
: ex
(CuA2)°~g(H')2"q Y C u , ~ '
(1)
( C u 2')aq(HA)2org Tcu ~"~HA
The distribution coefficient of metal is defined as:
DM: (M)°rg ,t°tal
(2)
(M)aq,total
A mathematical model of extraction equilibrium using the K-value method developed by Lee et al. [4] was used to analyze the experimental results. The equilibrium data obtained in this work and calculated following the procedure described by Lee et al. [4] are given in Table 1. The equilibrium constant of the overall copper extraction, Kex, was calculated to be 297 ± 5. The experimental and calculated values of the distribution coefficient are plotted in Figure 1. Good agreement between the calculated and experimental data is indicated by the standard deviation value of 0.139 between these two results.
tBeckman SpectramctdcsInc., Andover,Massachusetts
Solvent extraction equilibria TABLE 1
823
Experimental and calculated equilibrium data for the extraction of copper in the C n S O 4 - H 2 S O 4 - I t 2 0 - L I X 860-kerosene system. (Extractant concentration = 0.036
mol/L.) Experimental Conditions
No.
I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
(pI'I)i,~a
1.84 1.90 2.06
(C u)i,al----~ (Cu),q,t,~ mol/L mol/L 0.008 0.007
2.07 2.09 2.27 2.29 2.35
2.99 3.22 4.12
0.008 0.004 0.007 0.008 0.008 0.012 0.017 0.018 0.019 0.020 0.021 0.022 0.023 0.008
K~
Log(Du.~, ) Log('Du.,~)
1.51 × 10-4 1.75 × 10-4 1.46 × 10-4
302 297 297
1.69 1.63 1.84
1.55 1.64 1.90
1.06 × 10-4 1.04 × 10-4 1.06 × 10-4 1.00 X 10-4 3 . 9 0 x 10-s 1.31 × 10-4 1.60x 10.5 3.00 × 10-5 4.50 × 10.5 4.60 × 10"s 1.60 × 10.4 7.90 × 10-4 2.36x10- 3 2.15 x 10.3 3.93 X 10.3 4.72 X 10.3 5.51 × 10.3 6.30 × 10-3 2.60 x 105 2.90 x 10"s 1.80 x 10s 3.70 x 10"s
297 297 297 297 297 297 296 297 296 297 295 296 298 297 299 298 297 297 297 297 297 297
1.84 1.85 1.84 1.87 2.31 1.76 2.36 2.38 2.24 2.22 1.87 1.30 0.83 0.71 0.61 0.53 0.47 0.41 2.46 2.42 2.61 2.32
1.90 1.90 1.90 1.90 2.04 2.10 2.52 2.24 2.12 2.14 1.99 1.08 0.97 0.69 0.52 0.42 0.64 0.52 2.47 2.49 2.57 2.55
Design of a continuous extraction process requires information on equilibrium isotherm. The extraction of copper is usually carried out in the pH range from 1 to 3 in commercial processes [6, 7]. In this study, an equilibrium isotherm was determined at a starting pH of 2.1 _+0.1. The concentration of the aqueous phase used in this study was low (in the range of 470 _+ 30 mg/L) because this study was concerned mainly with application to the treatment of low-concentration copper solutions. As a consequence the pH of the aqueous solution changed by less than 0.2 during extraction. The extraction isotherm data for CuSO4-H2SO4-H20--LIX 860--kerosene system obtained from the phase ratio variation method are shown in Table 2. Equilibrium was reached using a fresh organic solution as well as an organic solution initially containing copper to ascertain that true equilibrium was attained. The same equilibrium state was reached within ten minutes for every phase ratio.
824
D. Doungdeethaveemtana and H. Y. Sohn
0 0
0
u
o
!
2 Log(DM,exp)
Fig. 1
Comparison between calculated and experimental distribution coefficients for Cu extraction with LIX 860.
TABLE 2
Extraction isotherm data. (Initial concentration of Cu in aqueous solution = 492 mg/L Cu. Organic solution = 0.036 M LIX 860 in kerosene)
O/A Ratio
2/1 1/1 2/3 1/2 1/5 1/10
pH
Aqueous, mg/L Cu
Organic, mg/L Cu
1.95 2.06 1.95 2.01 1.95 2.08 2.10 2.17 2.23 2.35 2.34 2.48
1.83 1.44 2.92 2.94 9.64 10.3 38.5 40.5 284 287 390 390
245 245 489 489 724 723 907 903 1040 1020 1020 1020
Solvent extraction equilibria
825
Figure 2 represents the extraction isotherm for copper extraction with 0.036 M LIX 860 in kerosene. The equilibrium isotherm curve can be mathematically represented by the following equation: e
Co,g = e
C,q 3.4145x103, 9.3178x104C~
(mg/L)
(3)
The results of this work indicate that the K-value method of Lee et al. [4] can adequately describe the extraction equilibria in the CuSO4-H2SO4-H20-LIX 860-kerosene system, and that LIX 860 is a strong copper extractant based on the fact that the organic phase becomes saturated at relatively low copper concentration, as can be seen in Figure 2. 10(300'
11300'
r dII o
t
100 ¸
10 .1
1
I0
100
1000
Aq. Phase Cone., mg Cu/L
Fig.2
Equilibrium isotherm for copper extraction with LIX 860 in kerosene (pH = 2.1 _+0.1, temperature = 25°C).
CONCLUSIONS The compound LIX 860 is a strong copper extractant, for which the equilibrium constant of copper extraction, Kex, was determined to be 297_+5. The solvent extraction isotherm for the CuSO4-H2SO4-H20-LIX 860-kerosene system was obtained at 25°C and aqueous copper concentration below 500 mg/L. A previously developed thermodynamic model [4] closely predicted the experimentally measured distribution coefficients.
ACKNOWLEDGMENTS The authors wish to thank the Henkel Corp. for providing the extractant. DD received financial support from the Royal Thai Government during the course of this work. This work was also supported in part by the University of Utah Research Committee and the State of Utah Leasing Fund.
826
D. Doungdeethaveeratanaand H. Y. Sohn REFERENCES
1. .
3. 4. 5. 6. .
Sawistowski, H., in Mass Transfer with Chemical Reaction in Multiphase System, Vol, 1, pp. 667-676, Chemical Publishing Co., New York (1984). Russell, J.H. & Rickel, R.L., Solvent Extraction and Ion Exchange, 8, 855 (1990). Hoh, Y. & Bautista, R.G., Metall. Trans. B, 9B, 69 (1978). Lee, M.S., Lee, E.C. & Sohn, H.Y., J. Chem. Eng. Japan, 29, 781 (1996). Yoshizuka, K., Arita, H., Baba, Y. & Inoue, K., Hydrometallurgy, 23, 247 (1990). Lo, T.C., Baird, M.H.I. & Hanson, C., Handbook of Solvent Extraction, 131,235, 649, WileyInterscience, New York (1983). Kordosky, G.A., The Chemistry of Metals Recovery Using LIX® Reagents, Henkel Corporation, Tucson, Arizona (1990).
Correspondence on papers published in Minerals Engineering is invited, preferably by email to [email protected], or by Fax to +44-(0)1326-318352