A general model to account for the liquid/liquid kinetics of extraction of metals by organic acids

Abstract

A model based on two-film theory is developed for the case of the rate of extraction of a divalent metal from an aqueous acid phase with an organic acid HR held in a second immiscible solvent phase. The model involves a reaction zone of variable thickness so that the case of reaction at an interface of molecular dimensions can be accommodated as well as the case of reaction extending into the diffusion film on the aqueous side of the interface. Four parameters are used, one involving a partition coefficient for the acid, one involving diffusivities in the films together with the two-film mass-transfer coefficients. Rate data from three techniques used in laboratory liquid/liquid contacting are fitted by the model.