Ion interaction model applied to the CuSO4-H2SO4-H2O system at 25 °C

C. F. Baes, E. J. Reardon, Bruce A. Moyer

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Abstract

The modeling of aqueous mixtures of a bivalent metal sulfate and sulfuric acid according to the treatment of Pitzer is complicated by the formation of bisulfate ion and by the need to include the effects of unsymmetrical mixing of ions of like but unequal charge. Because of the economic importance of the recovery of copper by the leaching of its ores with sulfuric acid, it is especially important to improve estimates of Pitzer parameters for the CuSO4-H2SO4-H2O system. Accordingly, we have applied the Pitzer treatment to available osmotic, solubility, and emf data for this system, with inclusion of unsymmetrical mixing effects. We employed published parameters for the H2SO4-H2O system and evaluated literature data to obtain parameters for the CuSO4-H2O system. The best fits to the data for mixtures were given by parameter sets that, in addition to β(0)[Cu2+-HSO4-] and β(1)[Cu2+-HSO4-], included at least one other parameter. The best choice of one was ψ[Cu2+-H+-HSO4-], and the best choice of two additional parameters was θ[Cu2+-H+] and ψ[Cu2+-H+-HSO4-]. The resulting mean activity coefficient (γ±) of CuSO4 at trace concentrations shows a dependence on sulfuric acid concentration quite similar to that found previously for FeSO4 and for NiSO4. For such solutions, predicted values of the quotient (γ±2)CuSO4/(γ ±3)H2SO4, a measure of the extractability of copper, are in reasonably good agreement with a previous prediction based on the extraction of Cu(II) by didodecylnaphthalenesulfonic acid in toluene.

Original languageEnglish
Pages (from-to)12343-12348
Number of pages6
JournalJournal of Physical Chemistry
Volume97
Issue number47
DOIs
StatePublished - 1993

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