740
Ind. Eng. Chem. Res. 2000, 39, 740-745
Modeling of Copper(II) and Zinc(II) Extraction from Chloride Media with KELEX 100 Mariusz B. Bogacki,† Svetlana Zhivkova,‡ George Kyuchoukov,‡ and Jan Szymanowski*,† Institute of Chemical Technology and Engineering, Poznan University of Technology, Poznan, Poland, and Institute of Chemical Engineering, Bulgarian Academy of Science, Sofia, Bulgaria
The extraction of copper(II) and zinc(II) from acidic chloride solutions with protonated Kelex 100 (HL) was studied and the extraction isotherms were determined for systems containing individual metal ions and their mixtures. A chemical model was proposed and verified. It considers the coextraction of the following species: MCl4(H2L)2, MCl4(H2L)2‚HCl, MCl3(H2L), ML2, and H2L‚HCl. Zinc(II) is extracted as the metal ion pairs, while copper(II) can be extracted as the metal ion pair and the chelate. The model can be used to predict the effect of experimental conditions on extraction and coextraction of the metal ions considered. Introduction In recent years extraction of metal ions from chloride media attracted the attention of various research centers, including those in industry and universities. As a result, new reagents were proposed for selective recovery of copper(II) and zinc(II) from solutions containing 4-6 M Cl-, e.g., ACORGA CLX 50 and ACORGA ZNX 50 proposed by Zeneca Specialties.1-9 They contain pyridine and bibenzimidazole derivatives, respectively, as the active substance. Various aspects of the extraction with models of these reagents were discussed by us.10-18 Extraction with these reagents has both positive and negative features. Large amounts of metal ions can be extracted with these extractants because the extraction is not sensitive to the acidity of the aqueous phase and free proton cations are not liberated. The stripping can be easily carried out with hot water. It, however, means that the electrowinning must be carried out from chloride media, giving undesired granules of metal instead of their sheets as in the classical electrowinning from the sulfate media. The change of the system from chloride into sulfate in the extraction-stripping process was also considered. It can be achieved using mixed reagents: a basic reagent and a chelating reagent,19-22 a solvating reagent and a chelating compound,23,24 or a bifunctional extractant.25-28 Kelex 100 and Lix 26, which contain 7-alkyl8-hydroxyquinoline (HL) as the active substance, can be considered as such a bifunctional extractant.28 It can react as a basic reagent transferring metal chlorocomplexes into organic phase, e.g., in the form MCl4(H2L)2. Then chloride ions can be qualitatively washed out by scrubbing with water at appropriate pH with the simultaneous transfer of metal ion from the ion pair into the chelate ML2. As a result, a traditional stripping with sulfuric acid of appropriate concentration and then the classical electrowinning can be carried out. The main drawback of such processes is the insufficient selectivity of extraction with basic reagents. They * To whom correspondence should be sent. E-mail:
[email protected]. † Poznan University of Technology. ‡ Bulgarian Academy of Science.
react with each metal, which can form negatively 2charged chlorocomplexes, e.g., MCl3 and MCL4 . The reaction with neutral MCl2 is also possible. Our work indicates, however, that an appropriate selectivity of such process can be achieved and various metal ions can be separated when appropriate conditions for extraction, scrubbing, and/or stripping are selected. To obtain it, appropriate chemical models can be elaborated. The aim of this work is to propose and verify the model for extraction of zinc(II) and copper(II) present either alone or together in the aqueous feed. Experimental Section Kelex 100 was kindly supplied by Shering A. G. Low aromatic kerosene was used as a diluent and decanol as a modifier. The organic phase used for extraction contained 20 v/v % Kelex 100, 15 v/v % octanol, and 65 v/v% kerosene. Prior to the first extraction experiment, the organic solution was conditioned by washing three times with water and then 3 M hydrochloric acid to remove water-soluble impurities and to obtain the full protonation of Kelex 100. The aqueous feed contained only zinc(II) and copper(II) or mixtures of these metal ions. The chloride concentration in the feed was adjusted with lithium chloride and the acidity with hydrochloric acid. Copper(II) and zinc(II) were introduced in the form of CuCl2 and ZnCl2. The extraction was carried out at room temperature in separatory funnels. Equilibrium was achieved in each case owing to an intensive mechanical mixing carried out for 15 min. The feed (100 cm3) was extracted with 50 cm3 of the Kelex 100 solution. The raffinate (5 cm3) was taken for analysis, and 95 cm3 of the raffinate was used as a feed for next extraction. The procedure was repeated several times. In each case 50 cm3 of the Kelex 100 solution was used. The extract was scrubbed with water at adjusted pH and then with sulfuric acid. H2SO4 (2.8 M) was used to achieve the complete stripping. NaCl solution (5 M) was used for the conditioning of the organic phase, i.e., for the transfer of Kelex 100 hydrosulfate into the hydrochloride form. After separation of phases, the contents
10.1021/ie990413c CCC: $19.00 © 2000 American Chemical Society Published on Web 02/09/2000
Ind. Eng. Chem. Res., Vol. 39, No. 3, 2000 741 Table 1. Chlorocomplex Formation Constants for Zinc(II)29 and Copper(II)10 formation constant
unit of βi
Zn(II)
Cu(II)
ln β1 ln β2 ln β3 ln β4
M-1 M-2 M-3 M-4
0.39 0.48 0.07 0.58
-0.05 0.80 -1.30 -2.80
of metal ions, chloride, and proton were determined in the aqueous phases and the composition of the organic phase was estimated from the mass balance. The content of metal ions present separately in the aqueous phases was determined by titration with EDTA in the presence of the following indicators: PAR for copper(II) and PAN for zinc(II). The total concentration of both metal ions was determined in the same way in the presence of a mixture of both indicators. The content of copper(II) was then determined by iodometric titration. The content of chloride and proton ions was determined by potentiometric titration with silver nitrate and sodium hydroxide, respectively. Results and Discussion Both zinc(II) and copper(II) can form various chlorocomplexes with the relative content dependent on the concentration of chloride ions in the aqueous phase:
M2+ + nCl- ) MCl2-n n βn )
[MCl2-n n ] 2+
- n
[M ][Cl ]
(1) (2)
The values of formation constants depend significantly on the composition of the aqueous phase, which can be quantified by the ionic strength and/or water activity. It was impossible to keep these parameters constant in our experiments. Moreover, addition of other electrolytes, such as sodium and magnesium nitrates, would be necessary. Therefore it was decided to consider the βn values, used previously for systems containing high concentrations of chloride ions (Table 1).10,11,14,27,29 Figure 1 shows the content of various chlorocomplexes of Zn(II) and Cu(II) present simultaneously ([Cu(II)]T ) [Zn(II)]T ) 0.5 M, where the subscript T denotes the total concentration) in the aqueous phase. It is obvious that zinc(II) forms more stable chlorocomplexes than copper(II). In the most important region of chloride concentration ([Cl-] ) 5-7 M), zinc(II) is mainly present in the form of the anionic chlorocomplex ZnCl24 . The content of ZnCl3 is also significant. However, copper is mainly present in the form of the neutral chlorocomplex CuCl2. The content of anionic copper chlorocomplexes is significant, but the presence of cationic species CuCl+ and Cu2+ cannot be neglected. Thus, the results suggest that copper(II) and zinc(II) can be extracted in the forms of different complexes. Kelex 100 can form both the ion pairs with metal chlorocomplexes and the chelates with metal cations. In such a case equilibrium between protonated and deprotonated forms of Kelex 100 must be considered. Additionally, at high acidities and high chloride concentration, the bonding of the second molecule of the hydrochloric acid by the protonated Kelex 100 is possible.25,30,31 The bonding of the hydrochloric acid to the extracted ion pair MCl4(H2L)2 was also taken into consideration.
Figure 1. Effect of chloride concentration on the content of various metal chlorocomplexes. Cu(II) and Zn(II) present simultaneously in the aqueous phase, [Cu(II)]T ) [Zn(II)]T ) 0.5 M. Chlorocomplex formation constants are given in Table 1.
The following set of chemical equilibrium was considered:
1 1 MCl2a + MCl24a + 2H2LClo ) MCl4(H2L)2o + Cla 2 2 (3) MCl23a + H2LClo ) MCl3H2Lo + Cla
(4)
+ M2+ a + 2H2LClo ) ML2o + 4Ha + 2Cla
(5)
H+ a + Cla + H2LClo ) H2LCl‚HClo
(6)
H2LClo ) HLo + H+ a + Cla
(7)
MCl4(H2L)2o + H+ a + Cla ) MCl4(H2L)2‚HClo (8)
with the following equilibrium constants
KA )
[MCl4(H2L)2]o[Cl-]o 1/2 2 [MCl2] 1/2 a [MCl4] a [H2LCl] o
[MCl3H2L]o[Cl-]a
KB )
KC )
KD )
[MCl3 ]a[H2LCl]o
[ML2]o[H+] 4a[Cl-] 2a [M2+]a[H2LCl] 2o [H2LCl‚HCl]o [H2LCl]o[H+]a[Cl-]a
KE )
KF )
[H+]a[Cl-]a[HL]o [H2LCl]o
[MCl4(H2L)‚HCl]o [MCl4(H2L)]o[H+]a[Cl-]a
(9)
(10)
(11)
(12)
(13)
(14)
where a and o denote aqueous and organic phase, respectively.
742
Ind. Eng. Chem. Res., Vol. 39, No. 3, 2000
Reaction 3 takes into account two different options: MCl24a + 2H2LClo ) MCl4(H2L)2o + 2Cla
(15)
MCl2o + 2H2LClo ) MCl4(H2L)2o + 2Cla
(16)
This means that the reactions of the two negative chlorocomplexes MCL24 (eq 15) and MCl3 (eq 4) and of the neutral chlorocomplex MCl2 (eq 16) with the protonated KELEX 100 are considered. Depending on the extraction conditions, especially metal type and the concentrations of chloride and proton, the contributions of these three reactions in the total extraction can be different. The same concerns the formation of the chelate (eq 3). Low concentrations of proton and chloride ion form conditions suitable for this reaction. The formation of the chelate is more probable for copper(II) with respect to zinc(II). The formation of the chelate needs the deprotonation of KELEX 100 (eq 7). At high concentrations of proton and chloride ions, i.e., in the case considered in this work, the protonated KELEX 100 can bind the second molecule of the hydrochloric acid (eq 6). Hydrochloric acid molecules can also be bound to the metal ion pair MCl4(H2L)2 (eq 8). Additionally, three or four equations for mass balance of metal (Zn(II) or Cu(II), or Zn(II) and Cu(I), respectively), chloride ions, and protons ions in the organic phase were formulated
Table 2. Estimated Equilibrium Constantsa equation no.
unit of Ki
copper(II)
zinc(II)
3 4 5 6 7 8
M-1
60.8 0 155.4 0.024 0 5.34
458 89.6 0 0.095 0 92.0
M4 M-2 M2 M-2
a Ranges of studied concentrations: [M2+] ) 0.01-0.97 M, [Cl-] ) 4.53-7.50 M, and [H+] ) 0.55-1.80 M. Variance of model σ2 ) 0.0071.
Figure 2. Comparison of the metal content in the organic phase determined experimentally (points) and estimated from the model (lines). Cu, 9; Zn, /. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Cl-] ) 4.5-7.5 M, [H+] ) 0.5-1.8 M.
[M]o,T ) [ML2]o + [MCl3H2L]o + [MCl4(H2L)2]o + [MCl4(H4L)2‚HCl]o (17) [Cl]o,T ) [H2LCl]o + 2[H2LCl‚HCl]o + 3[MCl3H2L]o + 4[MCl4(H2L)2]o + 5[MCl4(H2L)2‚HCl]o (18) [H]o,T ) [HL]o + 2[H2LCl]o + 3[H2LCl‚HCl]o + 2[MCl3H2L]o + 4[MCl4(H2L)2]o + 5[MCl4(H2L)2‚HCl]o (19) where the double subscript “o,T” denotes the total concentration of the species considered determined experimentally in the organic phase. The set of eqs 1-19 was solved by the least-squares method. This means that the equilibrium and mass balance equations given above both for Zn(II) and Cu(II) were taken under consideration simultaneously. The variance of the model σ2 equals 0.0071, and the correlation coefficient amounts to 0.997, proving the statistical validity of the model. Two different series of extraction experiments were carried out. In the first series the feed solutions contained only copper(II) or zinc(II) and the results obtained were used to compute the corresponding extraction constants (Table 2). Significantly different values of the equilibrium constants were obtained for zinc(II) and copper(II). Zinc(II) is only extracted by the ion exchange mechanism according to eqs 3 and 4 and KA > KB. However, copper can be extracted both by the chelating mechanism (eq 5) and by the ion exchange mechanism (eq 3) and KC > KA. These conclusions are in agreement with our previous work and with different abilities of metal ions considered to form chlorocomplexes. Zinc(II) forms more stable chlorocomplexes and at lower concentration of
Figure 3. Comparison of the chloride content in the organic phase determined experimentally (points) and estimated from the model (lines). Cu, 9; Zn, /. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Cl-] ) 4.5-7.5 M, [H+] ) 0.5-1.8 M.
chloride ions than does copper(II). At the extraction conditions studied, i.e., relatively high concentrations of hydrogen and chloride ions, the equilibrium of reagent deprotonation (eq 7) is totally shifted toward the hydrochloride form. Thus, the deprotonation of Kelex 100 is not observed. The formation of the adduct between the Kelex 100 hydrochloride and hydrochloride acid is observed again in agreement with the literature data.25,30,32 However, it is very interesting that the model predicts also the bonding of the hydrochloride acid molecule with the extracted metal ion pair (eq 8). Moreover, this reaction seems favored, especially for the extraction of zinc(II), in comparison to reaction 6. Figures 2-4 demonstrate the fitting of the model (solid and dashed lines) to the experimental data (points). Satisfactory agreement is achieved. Some deviations are only observed for the proton content in the organic phase. The distribution of metal in various complexes in the organic phase is given in Figures 5 and 6. Under the conditions studied, zinc(II) is present in the organic
Ind. Eng. Chem. Res., Vol. 39, No. 3, 2000 743
Figure 4. Comparison of the proton content in the organic phase determined experimentally (points) and estimated from the model (lines). Cu, 9; Zn, /. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Cl-] ) 4.5-7.5 M, [H+] ) 0.5-1.8 M.
Figure 7. Extraction isotherms. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Zn(II)]:[Cu(II)] ) 0.94:0.36 mol/mol, [Cl-] ) 7.51 M, and [H+] ) 1.76 M.
Figure 8. Extraction isotherms. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Zn(II)]:[Cu(II)] ) 0.36:0.94 mol/mol, [Cl-] ) 7.49 M, and [H+] ) 1.79 M. Figure 5. Estimated distribution of copper(II) in various complexes in the organic phase: 1, CuCl4(H2L)2; 2, CuCl4(H2L)2‚HCl; 3, CuCl2; 4, total content of copper(II). Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Cl-] ) 4.53-7.36 M, [H+] ) 0.55-1.74 M.
Figure 9. Extraction isotherms. Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Zn(II)]:[Cu(II)] ) 0.94:0.36 mol/mol, [Cl-] ) 7.24 M, and [H+] ) 1.89 M. Figure 6. Estimated distribution of zinc(II) in various complexes in the organic phase: 1, ZnCl4(H2L)2; 2, ZnCl3H2L; 3, ZnCl4(H2L)2‚ HCl; 4, total content of zinc(II). Organic phase: 20 v/v% protonated KELEX 100, 15 v/v% octanol, and 65 v/v% kerosene. Aqueous feed: [Cl-] ) 4.81-7.50 M, [H+] ) 0.74-1.80 M.
phase in comparable amounts as ZnCl4(H2L)2, ZnCl3(H2L), and ZnCl4(H2L)2‚HCl. Copper(II) is mainly present in the form of CuCl4(H2L)2 and CuCl4(H2L)2‚HCl, and only in negligible amounts as CuL2. The small quantities of the chelate are the result of high concentrations of chloride and hydrogen cations. The former promotes the formation of copper chlorocomplexes and then the ion pair. The latter prohibits both the reagent deprotonation and the formation of the chelate. Thus, although the extraction constant of reaction 5 is the highest, copper is mainly bonded into ion pairs. In the next step of studies, the aqueous feeds containing simultaneously Cu(II) and Zn(II) at three different
molar ratios equal to 2.67:1, 1:1, and 1:2.67 were used. The chloride and hydrogen ion concentrations were similar to those used in experiments with individual metal ions. The proposed model (eqs 1-19) and the extraction constants estimated for the systems containing individual metal ions (Table 2) were used to predict the extraction of both metals. The results presented in Figures 7-10 indicate agreement between the experimental and calculated concentrations of metal ions in the extract and raffinate. It proves the validity of the proposed model and its usefulness to predict the results of extraction in the systems containing both zinc(II) and copper(II). Moreover, the model can be used to predict the influence of the experimental conditions, i.e., the concentrations of proton and chloride ions changed in a relatively broad range, on the extraction of both individual metal ions and their mixtures.
744
Ind. Eng. Chem. Res., Vol. 39, No. 3, 2000
Figures 7 and 8 show the concentrations of Zn(II), Cu(II), and their sum in the extractant versus the total concentrations of metal ions in the raffinate. As in previous figures, a high concentration of metal ions in the raffinate corresponds to the high concentration of both chloride and hydrogen ions. The isotherms have a characteristic shape. The additional Figure 9 is also presented to make the results better understandable. The figure presents the concentrations in the raffinate, i.e., Zn(II) in extract versus Zn(II) in raffinate, and Cu(II) in extract versus Cu(II) in raffinate. Thus, Figures 7 and 9 should be interpreted simultaneously. They show that the extraction equilibrium favors the extraction of zinc(II). In the countercurrent process, zinc(II) is first extracted and its concentration in the aqueous phase sharply decreases. No copper would be expected in the highly loaded organic phase. The coextraction of copper(II) is expected only in the region where an atypical shape of the isotherm (a decreasing part) is observed. In each case considered a typical character of the isotherm is observed for zinc(II) and an atypical one for copper(II). In the latter case the isotherm assumes a typical character (an increasing part of the curve) in the region where zinc(II) is not present in the raffinate (i.e., Zn(II) was already almost totally extracted in the previous steps). The declining part of the isotherm determined for copper corresponds to the region of zinc(II) extraction. Thus, zinc(II) is first extracted from the mixtures containing both metal ions. As a result, its concentration in the extract decreases to the value near zero when copper is still present in the raffinate in the amount approximately 0.05, 0.4, and 0.7 M for [Zn]:[Cu] in the feed equal to 2.67:1, 1:1, and 1:2.67, respectively. Conclusions The extraction of copper(II) and zinc(II) present alone or simultaneously in the aqueous feed in acidic chloride solutions with Kelex 100 (HL) can be modeled assuming the coextraction of the following species: MCl4(H2L)2, MCl4(H2L)2‚HCl, MCl3(H2L), ML2, and H2L‚HCl. Zinc(II) is extracted by the protonated Kelex 100 only as metal ion pairs, while copper(II) can also be extracted as the chelate. Agreement of the model with the experimental data is observed. The model can be used to predict the extraction results under various extraction conditions, for systems containing only zinc(II) or copper(II) and their mixtures. Acknowledgment M.B.B. and J.S. are thankful for Grant No. 3T09B05114 from the Polish Research Committee KBN. G.K. thanks the Polish Foundation for Science Support: “Kasa im. Jo´zefa Mianowskiego, Fundacja Popierania Nauki”, Poland, for financial support to visit Poznan University of Technology. Literature Cited (1) Dalton, R. F.; Burgess, A.; Quan, P. M. ACORGA ZNX50s A New Selective Reagent for the Solvent Extraction of Zinc from Chloride Leach Solutions. Hydrometallurgy 1992, 30, 385. (2) Dalton, R. F.; Diaz, G.; Price, R.; Zunkel, A. D. The CUPREX Metal Extraction Process: Recovering Copper from Sulphide Ores. J. Met. 1991, 43, 51. (3) Dalton, R. F.; Price, R.; Quan, P. M.; Steward, D. Extraction of Metal Values. Eur. Pat. Spec. EP 57,797, 1982.
(4) Dalton, R. F.; Price, R.; Hermana, E.; Hoffmann, B. Cuprexs New Chloride-Based Hydrometallurgy To Recover Copper from Sulphide Ores. Miner. Eng. 1988, 40, 24. (5) Devonald, D. P.; Nelson, A. J.; Quan, P. M.; Steward, D. Process for the Extraction of Metal Values and Novel Extractants. Eur. Pat. EP 196,153 B1, 1986; U.S. Patent 4,696,801, 1987; U.S. Patent 4,822,880, 1989. (6) Alderman, A.; Cox, M.; Dalton, R. F. Hollow Fibre Supported Liquid Extraction of Copper from Chloride Media Using ACORGA CLX50. Proceedings of the International Solvent Extraction Conference, ISEC’93; Logsdail, D. H., Slater, M. J., Eds.; Elsevier Applied Science: London, 1993; Vol. 3, p 883. (7) Soldenhoff, K. M. Solvent Extraction of Copper(II) from Chloride Solutions by Some Pyridine Carboxylate Esters. Solvent Extr. Ion Exch. 1987, 5, 833. (8) Bart, H. J.; Dalton, R. F.; Hillisch, W.; Hughes, M. A.; Slater, M. J. ACORGA CLX50sA Novel Reagent for Solvent Extraction of Copper. A Kinetics Study. Proceedings of the International Solvent Extraction Conference, ISEC′96; Shallcross, D. C., Paimin, R., Prvcic, L. M., Eds.; The University of Melbourne: Melbourne, Australia, 1996; p 845. (9) Aquilar, M.; Valiente, M.; Massana, A.; Coello, J.; Aparico, J. L.; Fernandez, L. A.; Muhammed, M. Extraction of Divalent Metals from Chloride Solutions. Proceedings of the International Solvent Extraction Conference, ISEC’86, Munich, Germany, DECHEMA: Frankfurt am Main, 1986; Vol. 2, p 239. (10) Cote, G.; Jakubiak, A.; Bauer, D.; Szymanowski, J.; Mokili, B.; Poitrenaud, C. Modeling of Extraction Equilibrium for Copper(II) Extraction by Pyridinecarboxylic Acid Esters from Concentrated Chloride Solutions at Constant Activity of Water and Constant Total Concentration of Ionic or Molecular Species Dissolved in Aqueous Solution. Solvent Extr. Ion Exch. 1994, 12, 99. (11) Cote, G.; Jakubiak, A. Modelling of Extraction Equilibrium for Zinc(II) Extraction by a Bibenzimidazole Type Reagent (ACORGA ZNX50) from Chloride Solutions. Hydrometallurgy 1996, 43, 265. (12) Bogacki, M. B.; Jakubiak, A.; Cote, G.; Szymanowski, J. Dialkyl Pyridinedicarboxylates Extraction Abilities toward Copper(II) from Chloride Solutions and Its Modification with Alcohols. Ind. Eng. Chem. Res. 1997, 36, 838. (13) Bouvier, C.; Cote, G.; Cierpiszewski, R.; Szymanowski, J. Influence of Salting-Out Effects, Temperature and the Chemical Structure of the Extractant on the Rate of Copper(II) Extraction from Chloride Media with Dialkyl Pyridine Dicarboxylates. Solvent Extr. Ion Exch. 1998, 16, 1465. (14) Bogacki, M. B.; Jakubiak, A.; Cote, G.; Szymanowski, J. Dialkyl Pyridinedicarboxylates Extraction Abilities toward Copper(II) from Chloride Solutions and Its Modification with Alcohols. Ind. Eng. Chem. Res. 1997, 36, 838. (15) Borowiak-Resterna, A.; Blaszczak, J.; Bogacki, M. B.; Szymanowski, J. Interfacial Activity of Model Hydrophobic Pyridinecarboxamides. Solvent Extr. Ion Exch. 1997, 15, 1051. (16) Borowiak-Resterna, A. Extraction of Copper from Acid Chloride Solutions by N-alkyl- and N,N-Dialkyl-3-pyridinecarboxamides. Solvent Extr. Ion Exch. 1994, 12, 557. (17) Voelkel, A.; Borowiak-Resterna, A. Solubility and Polarity Parameters for Pyridine Carboxamides and Their Complexes with Copper(II) as Determined by Inverse Gas Chromatography. J. Chromatogr. A 1996, 740, 253. (18) Borowiak-Resterna, A. Extraction of Copper(II) from Acid Chloride Solutions by N-Dodecyl and N,N-Dihexyl Pyridecarboxamides. Solvent Extr. Ion Exch. 1999, 17, 133. (19) Kyuchoukov, G.; Mihaylov, I. A Novel Method for Recovery of Copper from Hydrochloric Acid Solutions. Hydrometallurgy 1991, 27, 361. (20) Kyuchoukov, G.; Mishonov, I. A New Extractant Mixture for Recovery of Copper from Hydrochloric Etching Solution. Solvent Extr. Ion Exch. 1993, 11, 555. (21) Mishonov, I.; Kyuchoukov, G. Separation of Copper and Zinc During their Transfer from Hydrochloric Acid to Sulphuric Acid Medium Using a Mixed Extractant. Hydrometallurgy 1996, 41, 89. (22) Kyuchoukov, G.; Mishonov, I. On the Extraction of Copper and Zinc from Chloride Media with Mixed Extractant. Solvent Extr. Res. Dev., Jpn. 1999, 6, 1. (23) Fletcher, A. W.; Sudderth, R. B.; Olafson. S. M. Combining Sulfate Electrowinning with Chloride Leaching. J. Met. 1991, 43, 57.
Ind. Eng. Chem. Res., Vol. 39, No. 3, 2000 745 (24) Jakubiak, A.; Cote, G.; Szymanowski, J. Extraction of Zinc(II) from Chloride Media with a Mixture of Acorga ZNX 50 and LIX 54. Solvent Extr. Res. Dev., Jpn 1999, 6, 24. (25) Kyuchoukov, G.; Kounev, R. Copper Transfer from Hydrochloric Acid into Sulphuric Acid Solution by Means of Kelex 100. Hydrometallurgy 1994, 35, 321. (26) Kyuchoukov, G.; Jakubiak, A.; Szymanowski, J. Zinc (II) Extraction from Chloride Solutions by Kelex 100. Solvent Extr. Res. Dev., Jpn. 1997, 4, 1. (27) Kyuchoukov, G.; Jakubiak, A.; Szymanowski, J.; Cote, G. Extraction of Zinc(II) from Highly Concentrated Chloride Solutions by KELEX 100. Solvent Extr. Res. Dev., Jpn. 1998, 5, 170. (28) Demopoulus, G. P.; Paskouleli, G.; Ritcey, G. M. Proceedings of the International Solvent Extraction Conference, ISEC’86, Munich, Germany, DECHEMA: Frankfurt am Main, 1986; Vol. 2, p 581. (29) Liddell, K. C.; Bautista, R. G. Equilibrium Species Concentrations in the Aqueous HCl-NaCl-ZnCl2 and HCl-NaCl-
CdCl2 Systems: The Effect of Ionic Strength. Hydrometallurgy 1988, 11, 349. (30) Benguerel, E.; Demopoulos, G. P.; Cote, G.; Bauer, D. An Investigation on the Extraction of Rhodium from Aqueous Chloride Solution with 7-Substituted 8-Hydroxyquinolines. Solvent Extr. Ion Exch. 1994, 12, 497. (31) Cote, B.; Demopoulos, G. P. New 8-Hydroxyquinoline Derivative Extractants for Platinum Group Metal Separation. I. Characterization and HCl Extraction. Solvent Extr. Ion Exch. 1993, 11, 349.
Received for review June 10, 1999 Revised manuscript received December 2, 1999 Accepted December 11, 1999 IE990413C
