Kinetics of the recovery of Cd from highly concentrated aqueous solutions by non-dispersive solvent extraction

In this paper, the kinetics of the non-dispersive extraction and back-extraction of cadmium from high concentration aqueous solutions using D2EHPA as selective extractant are reported. Batch experiments were performed in order to analyse the influence of the initial Cd concentration in the feed, organic and back-extraction phases. The proposed kinetic model consists of a system of partial differential and algebraic equations describing the mass balances of Cd in the fluid phases of the hollow-fibre contactors and homogenisation tanks. The main hypothesis is that membrane mass transport controls the extraction kinetics. Two design parameters K-m, membrane mass transport coefficient, and K-eq, equilibrium parameter of the extraction reaction have been calculated from the correlation of the experimental results by the reported model. The comparison of experimental and simulated data confirmed the validity of the kinetic analysis. (C) 2001 Elsevier Science B.V. All rights reserved.