Effect of paraffin and surfactant on coupled transport of cadmium(II) ions through liquid membranes

The transport of Cd(II) ions from an aqueous feed chloride solution to an ammonium acetate stripping solution through a supported liquid membrane containing tri-n-octylamine (TOA) in xylene has been examined. The influence of stirring rate, carrier concentration, stripping agent and H+ concentration in the feed solution was investigated. The transport of Cd(II) ions is coupled by the co-transport of protons. The kinetics of transport could be analyzed in the formalism of two consecutive irreversible first-order reactions, considering both extraction and stripping reactions. The pseudo-first-order rate constants of interfacial reactions in membrane transport are determined with a bulk liquid membrane based on paraffin and the surfactant Span-80. The experimental results show that the effect of paraffin or surfactant in the membrane is different for the interfacial reactions of extraction and shipping. (C) 2000 Elsevier Science B.V. All rights reserved.