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-extra ction of cadmium from high concentration aqueous solutions using D2EHPA as selective extractant are reported. Batch experiments were performed in orde r to analyse the influence of the initial Cd concentration in the feed, org anic and back-extraction phases. The proposed kinetic model consists of a s ystem of partial differential and algebraic equations describing the mass b alances of Cd in the fluid phases of the hollow-fibre contactors and homoge nisation tanks. The main hypothesis is that membrane mass transport control s the extraction kinetics. Two design parameters K-m, membrane mass transpo rt coefficient, and K-eq, equilibrium parameter of the extraction reaction have been calculated from the correlation of the experimental results by th e reported model. The comparison of experimental and simulated data confirm ed the validity of the kinetic analysis. (C) 2001 Elsevier Science B.V. All rights reserved.