Kinetics and mechanism of interfacial reactions in the solvent extraction of copper

Abstract

The rotating-diffusion-cell technique for studying reactions at liquid/liquid interfaces has been applied to the study of the kinetics and mechanism of the extraction of Cu²⁺, using an oxime ligand. The technique has been extended by using a ring electrode in the ring–disc configuration to measure the flux of Cu²⁺ when it is stripped from the organic phase into strong acid. Both extraction and stripping reactions have been studied at various acid concentrations. In the extraction direction the rate of reaction is first order in Cu²⁺ and first order in oxime at low concentrations of both reactants; at higher concentrations a limiting rate is observed. In the stripping direction a zero-order reaction is observed. This behaviour is interpreted in terms of an interfacial reaction in which the rate-limiting step is the attachment of the first oxime to Cu²⁺.