Kinetics and Mechanism of Copper Transfer by Hydroxy-Oximes in Three-Phase Liquid Systems

Abstract

A model of copper-facilitated transport in a three-liquid-phase pertraction system is proposed. The model takes into account the diffusional transport of copper species (ions and complexes) in all three liquids as well as the kinetics of chemical reactions. The latter, according to the model suggested, occurs in narrow reaction zones: aqueous layers adjacent to the donor membrane and acceptor-membrane interfaces. Experiments were carried out in a two-compartment agitated diffusion cell with a bulk liquid membrane: a 5% (vol) solution of the commercial copper extractant LIX 860 in C₁₁-C₁₃ normal paraffins. The donor solution used contained 1 g/L copper and the acceptor liquid was a 4.5 N aqueous solution of sulfuric acid. On the basis of experimentally obtained pertraction curves and the model suggested, it was found that the overall rate of the process is controlled by the diffusion of copper ions in the donor phase as well as by copper-complex decomposition. By applying an optimization procedure, the mass transfer coefficients and the rate constants were evaluated under the experimental conditions of this study.