Prediction of Cu(II) Solvent Extraction Behavior with Hydroxyoxime in the Presence of Alkali-metal Chloride.

Abstract

A chemically based prediction method for the equilibrium distribution ratios has been described for the solvent extraction of Cu (II) with hydroxyoxime from the quaternary solutions of HX-CuX2-MXn-H2O, where X is a univalent anion and M is a cation. This method is characterized by the employment of Pitzer's estimation equations for the stoichiometric activity coefficients of the aqueous species and for the excess volume of the aqueous phase. In order to determine the accuracy of the computational results, extraction experiments have been performed using Acorga P-5100 as the extractant under various HCl and MCl (M=Li, Na, or K) concentrations with the constant initial CuCl2 concentration of 0.1mol·dm-3, exhibiting a gradual decrease in the distribution ratios with the increase in MCl. The degree of the decrease is independent of the species of M.The present method can predict the distribution ratios very accurately at least up to an MCl concentration of 3 mol·dm-3 when M is Li or Na. When M is K, the agreement is good within a limited MCl concentration range, which could be extended if mixing parameters-between MCl and CuCl2 for the activity coefficient estimation become available.The dependencies of the extraction behavior on the concentrations of hydrogen ions and alkali-metal chlorides were discussed in terms of the changes in the activity coefficients of cupric and hydrogen ions.