The mechanism of extraction of zinc(II) from aqueous chloride solutions into chloroform solutions of methyltrioctylammonium chloride

Abstract

The mechanism of the transfer of zinc(11) between 1.0 M HCl, 6.0 M HCl and 6.0 M LiCl and methyltrioctylammonium chloride in chloroform has been studied by using the single-drop technique. It is suggested that interfacial complexes are formed by fast ion-exchange reactions and that the rate-determining step, in the case of 1.0 M HCl and 6.0 M LiCl, involves the replacement at the interface of the complex R₂ZnCl₄ by two molecules of reagent from the bulk organic phase. For 6.0 M HCl the rate-determining step is the replacement of the interfacial complex RHZnCl₄ by one molecule of reagent from the bulk organic phase.

Support for this mechanism is obtained by comparing the extraction equilibrium constants for the complex R₂ZnCl₄ for 1.0 M HCl and 6.0 M LiCl from previous with the values calculated from the rate data.

Interfacial tension measurements have shown that the interface is saturated with reagent over the full range of concentrations studied.