4084
Ind. Eng. Chem. Res. 1998, 37, 4084-4089
Copper Extraction from Ammoniacal Solutions with LIX 84 and LIX 54 George Kyuchoukov,† Mariusz B. Bogacki,‡ and Jan Szymanowski*,‡ Institute of Chemical Engineering of Bulgarian Academy of Science, Sofia, Bulgaria, and Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Sktodowskiej - Curie 2, 60-965 Poznan, Poland
Extraction of copper from ammoniacal solutions with LIX 84 and LIX 54 used alone and their mixture was studied, and a chemical model was proposed and verified. The equilibrium extraction constant was correlated with the ionic strength. The effect is weak for the strong extractant LIX 84 and its mixture but very strong for the weak extractant LIX 54. LIX 54 acts as a modifier of LIX 84 by formation of 1:1 and 1:2 co-associates. Their structures were estimated by molecular modeling. Introduction LIX 84 and LIX 54, manufactured by Henkel, are well-established copper extractants.1 These agents exhibit various extraction abilities. LIX 84 is a modern strong extractant used for copper recovery from acidic sulfate solutions, whereas LIX 54 is a weak extractant used for copper recovery from ammoniacal solutions, including etching solutions obtained from print circuit board manufactures. LIX 84 and LIX 54 contain 2-hydroxy-5-nonylacetophenone oxime (1) and 1-phenyldecanone-1,3-diones (2)2-4 as the active substance, respectively.
The different extraction abilities of these reagents are caused by significantly various acidities of the phenolic group in LIX 84 and the aliphatic hydroxyl group in the enolic forms of LIX 54 (3).
It is well-known that the extraction abilities of hydroxyoxime extractants can be modified by compounds * Author to whom correspondence should be sent. E-mail:
[email protected]. † Institute of Chemical Engineering of Bulgarian Academy of Science. ‡ Institute of Chemical Technology and Engineering.
able to form hydrogen bonds with hydroxyoximes,1,5-8 for examples, nonylphenol, tridecanol, and hydrophobic esters used in commercial extractants produced by ZENECA SPECIALITIES. An addition of a modifier does not worsen significantly the extraction abilities but facilitates stripping. As a result, higher amounts of metal ion can be transferred from the feed to the final raffinate in the extractionstripping process. Hydroxyoximes with hydroxyl and oximino group associate in hydrocarbon diluents forming mainly the cyclic dimers. The co-association can also occur when two different hydroxyoximes are present in the hydrocarbon phase. As a result, a weak hydroxyoxime extractant can act as a modifier for a strong hydroxyoxime extractant, as was described by Henkel for mixtures of LIX 860 and LIX 65N.9 The recovery of copper from ammoniacal etching solutions has become an important process used in several small-scale installations. β-Diketones and hydroxyoximes (ACORGA and LIX reagents) are recommended as appropriate extractants. It is known, however, that hydroxyoximes transfer some amounts of ammonia to the organic phase, especially at higher pH (>9), due to the nonylphenol presence in the extractant and a low loading of the organic phase.10 The aim of this work was to study the extraction of copper from ammoniacal chloride solutions by LIX 84, LIX 54, and their mixture and to explain the observed extraction effects. Experimental Section LIX 84 and LIX 54 were kindly donated by Henkel. They are liquids and therefore they could be used without any diluent. Low aromatic kerosene was also used to obtain 50% (v/v) solutions. The initial aqueous feed contained: 134 ( 2 g dm-3 Cu2+, ∼4.8 M Cl-, and 8 ( 0.3 M NH3. Appropriate volumes of aqueous and organic phases were shaken for 5 min and separated, and the composition of the aqueous phase was determined. The raffinate was then used as a feed in the successive extraction step. Copper was stripped from the organic phase with 3.16 or 4.06 N H2SO4. Equal volumes of both phases were used.
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Ind. Eng. Chem. Res., Vol. 37, No. 10, 1998 4085
The extraction of copper with the discussed extractants can be described by the following equation
Cu(NH3)42+w + 2HLo ) CuL2o + 2NH4+w + 2NH3w (1) with the equilibrium constant:
Kex )
[CuL2]o[NH4+]w2[NH3]w2 [Cu(NH3)42+]w[HL]o2
(2)
On the other hand the process may be modeled in the following way:
Figure 1. Extraction isotherms for copper extraction with LIX 84 and LIX 54 and their 1:1 (v/v) mixture (100 and 50% denote undiluted reagent and the 50% solution in kerosene, respectively: (*) the aqueous feed was diluted with distilled water in different ratios.
Molecular modeling was used to obtain information on association in a manner similar to that reported previously.11 Low molecular 2-hydroxy-5-propylacetophenone oxime and 1-phenylhexane-1,3-dione were considered as models. Semiempirical PM3 calculations were carried out on an IBM PC computer using version 6.00 of MOPAC.12 The precise mode used set the convergence criteria for GNORM ) 0.01 and SFRT ) 0.00001. Starting geometry for calculations was obtained with Dreiding models and expressed in internal coordinates. The initial conformation used standard bond distances and bond angles. The angles of hydrogen bonded ligands were selected to produce tetrahedral association around given oxygen atoms, although these angles were always allowed to optimize. For each selected associate structure (i.e., number of associated molecules and position of hydrogen bonding), the optimized geometry of the associate was produced for which the minimum PM3 heat of formation was obtained. Stereo drawings of the optimized forms were displayed by the HyperChem-Release 3 for Windows program (Autodesk, Inc.). Results and Discussion Extraction isotherms are given in Figure 1. They indicate that LIX 84 is a significantly stronger extractant than LIX 54. Undiluted (abbreviated as 100% v/v) LIX 84 and LIX 54 can be loaded with copper up to 40.6 and 40.2 g dm-3, respectively, whereas their 50% (v/v) solutions in kerosene can be loaded with copper up to ∼24.4 and ∼21.9 g dm-3, respectively. The shapes of isotherms are significantly different, especially in the region of low copper concentration in the aqueous phase. The isotherms obtained for LIX 84 are very steep, especially when 100% LIX 84 is considered. As a result, the concentration of copper in the organic phase is high and the raffinate can contain only negligible amounts of copper. The isotherms obtained for LIX 54 achieve their asymptotic maximum loading only for copper concentration in the aqueous phase >80 g dm-3, and the copper concentration in the extract increases slowly for lower copper concentrations in the raffinate.
Cu2+w + 2HLo ) CuL2o + 2H+w
(3)
Cu2+w + iNH3w ) Cu(NH3)i2+w
(4)
where i ) 1, 2, 3, and 4, and
NH3w + H+w ) NH4+w
(5)
with the following equilibrium constants
[CuL2]o[H+]w2
K3 )
βi )
[Cu2+]w[HL]o2 [Cu(NH3)i2+]w
[Cu2+w][NH3]iw
K5 )
[NH4+]w [NH3]w[H+]w
(6)
(7)
(8)
and the mass balance equation of copper in the aqueous phase i)1
[Cut]w ) [Cu2+]w(1 +
∑4 βi[NH3]iw)
(9)
Thus,
K3 )
[CuL2]o[NH4+]w2
1
K52 [Cut]w[HL]o2[NH3]w2
i)1
(1 +
∑4 βi[NH3]iw)
(10)
At appropriate high ammonia concentrations, when i)1
∑4 βi[NH3]iw . 1
(11)
and i)1
β4[NH3]4w .
∑3 βi[NH3]iw
(12)
Equation 10 simplifies to
K3 ) As a result
β4 [CuL2]o[NH4+]w2[NH3]w2 K52
[Cut]w[HL]o2
(13)
4086 Ind. Eng. Chem. Res., Vol. 37, No. 10, 1998
Figure 2. Simulation of copper extraction equilibrium for various extraction constants and various concentrations of alkaline reagents (NH3 + NH4+); solid line, Kex ) 50; dotted line, Kex ) 5000; [NH3] + [NH4+] equal to 2, 3.2, 5, and 8 mol dm-3 for curves 1, 1a; 2, 2a; 3, 3a; and 4, 4a, respectively).
Figure 3. Comparison of copper concentration in the organic phase after extraction with the mixture of LIX 84 and LIX 54 (1: 1, v/v) determined experimentally (Cu found) and calculated according to the additive rule (Cu calculated).
log[CuL2]o ) log Kex + log[Cut]w + 2 log[HL]o 2 log[NH4+]w - 2 log[NH3]w (14) where
Kex ) K3K52β4-1
(15)
Equation 14 derived with some simplification, explains well the observed experimental effects. The amount of extracted copper and then the shape of the extraction isotherm depend on the relative values of various terms present in this equation. It is obvious that the extraction rises when the concentrations of copper and extractant increase and the concentrations of ammonium ion and ammonia fall. The observed effects depend, however, on the values of extraction constant Kex, which are relatively small for strong extractants (i.e., LIX 84) for which the extraction equilibrium constant achieved a high value. Figure 2 shows the effect of total ammonia concentration ([NH3] + [NH4+]) on the copper extraction equilibrium for two selected extraction constants (Kex ) 50 and Kex ) 5000 mol2 dm-6) that are characteristic of a weak and strong extractant, respectively. It is obvious that ammonia depresses the extraction of copper by the formation of the copper ammonia complexes in aqueous phase (eq 4). The effect is strong for low copper concentration (i.e., when a significant excess of ammonia is present in the aqueous phase) and falls when the copper concentration increases. The effect depends on the extraction equilibrium constant and significantly decreases when the extraction constant rises. Thus, the effect of the ammonia concentration on copper extraction is relatively small for the strong extractant LIX 84 in comparison with the weak extractant LIX 54. As a result, different shapes of isotherms are observed for LIX 84 and LIX 54. Moreover, a dilution of aqueous feed with distilled water in different ratios significantly improves copper extraction with LIX 54 (Figure 1). Such an approach permits a constant ratio between various species (Cu2+, Cl-, NH3, and NH4+) in the aqueous feed. The isotherm changes its character and becomes similar to that observed for LIX 84, that is, the isotherm becomes steep in the region of low copper concentrations in the aqueous phase and the maximum
Figure 4. Extraction equilibrium constants calculated according to the model determined by the set of eqs 3-15 (Kex values were calculated for each experimental point).
loading (∼40 g dm-3) of the organic phase is already obtained for a copper concentration in the raffinate of ∼20 g dm-3. The isotherm obtained for the mixture of LIX 54 and LIX 84 (1:1, v/v) lies between the isotherms obtained for LIX 54 (100%) and LIX 84 (100%) used alone. The concentrations of copper found in the organic phase in equilibrium with various copper concentrations in the aqueous phase are approximately equal to those calculated by the additive rule from appropriate values determined for LIX 84 and LIX 54 used alone (Figure 3). A negative deviation is observed for copper concentration 1; Figure 9). The results were obtained in a similar way to those presented in Figure 8 by adapting the slope of the operating line to the considered ratio of flows [w/o (2,7)]. Conclusions Copper extraction from ammoniacal solutions changes in the following order of extractants LIX 84 > LIX 84 + LIX 54 > LIX 54. These differences are important for low copper concentrations in the feed. LIX 54 acts as a modifier of LIX 84 by formation of 1:1 and 2:1 coassociates. The extraction ability of LIX 84 is slightly decreased but the stripping is facilitated. The extraction can be well modeled by the chemical model that takes into account the positive effect of the ionic strength. This effect is strong for LIX 54 and small for LIX 84 and the LIX 84 + LIX 54 (1:1, v/v) mixture. Acknowledgment M. B. Bogacki and J. Szymanowski are grateful for Grant No. 3T09B05114 from the Polish Research Committee KBN. Nomenclature Kex ) extraction equilibrium constant for eq 1 K3 ) extraction equilibrium constant for eq 2 K5 ) ammonia complex equilibrium constant βi ) ammonia complex formation constants ∆H ) heat of formation
Literature Cited (1) Szymanowski, J. Hydroxyoximes and Copper Hydrometallurgy; CRC: Boca Raton, FL, 1993.
(2) Dziwinski, E.; Szymanowski, J. Composition of Copper Extractant LIX 54-100. Solvent Extr. Ion Exch. 1996, 14, 219. (3) Mickler, W.; Uhlemann, E.; Herzschuh, R. Byproducts of Classical b-diketone Syntheses. J. Prakt. Chem. 1991, 334, 435. (4) Mickler, W.; Uhlemann, E.; Herzschuh, R.; Wenclawiak, B.; Plaggenborg, L. The Characterization of the Active Components in Commercial β-diketone-Type Extractants LIX 54 and MX 80A. Sep. Sci. Technol. 1992, 27, 1171. (5) Dalton, R. F. The Effect of Alkyl Phenols on the Copper Transfer Properties of Extractant ACORGA P-1. CIM Spec. Vol. 1979, 22, 40. (6) Majdan, M.; Sperline, R. P.; Gu, W.-G.; Yu, W.-H.; Freiser, H. Interaction of Long-Chain Alcohol “Modifiers” with LIX Solvent Extraction Reagents. Solvent Extr. Ion Exch. 1989, 7, 987. (7) Szymanowski, J. Physicochemical Modification of Extractants. Crit. Rev. Anal. Chem. 1995, 25, 143. (8) Szymanowski, J. Modifiers in Extraction Systems. Solvent Extr. Res. Dev. Jpn 1994, 1, 97. (9) Kordosky, G. A.; Sierakoski, J. M.; House, J. E. The LIX 860 Series: Unmodified Extraction Reagents. Proceedings of the International Solvent Extraction Conference, Denver, CO, 1983; p 191. (10) Flett, D. S.; Melling, J. Extraction of Ammonia by Commercial Copper Chelating Extractants. Hydrometallurgy 1979, 4, 135. (11) Bogacki, M. B.; Jakubiak, A.; Cote, G.; Szymanowski, J. Dialkyl Pyridinedicarboxylates Extraction Abilities towards Copper(II) from Chloride Solutions and its Modification with Alcohols. Ind. Eng. Chem. Res. 1997, 36, 838. (12) Steward, J. J. P. MOPAC v. 6.0. QCPE 455, University of Indiana, Bloomington, IN, 1990. (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) Ectraction from Chloride Media with Dialkyl Pyridine Dicarboxylates, submitted for publication in Solvent Extr. Ion Exch. (14) Bogacki, M. B.; Szymanowski, J. Association of Hydroxyoxime Extractant with Oxygen Containing Modifiers. Solvent Extr. Res. Dev., Jpn. 1996, 3, 10. (15) MECER-A Solvent Extraction Process for the Recovery of Ammoniacal Etching Liquors; Transaco MX International AB, Stockholm, Sweden.
Received for review March 26, 1998 Revised manuscript received July 5, 1998 Accepted July 12, 1998 IE980192V
