Iron(III) transport using a supported liquid membrane containing Cyanex 921

A study of iron(III) transport through a solid-supported liquid membrane us ing the phosphine oxide Cyanex 921 as carrier has been carried out using ba tch experiments. A model is reported describing the transport mechanism whi ch consists of a diffusion process through a source aqueous diffusion layer , a fast interfacial chemical reaction and diffusion of HFeCl4 . L-2 (L, th e extractant) through the membrane. The transport system is studied as a fu nction of several variables, such as the diluent of the organic phase, meta l concentration in the source phase, etc., along with the composition of th e receiving solution. The mass transfer coefficient was calculated from the model as 23 mu m/s and the thickness of the source aqueous boundary layer was calculated to be 44 mu m. The behaviour of Cyanex 921 has been studied with respect to other organophosphorus extractants and also the selectivity of the membrane-carrier system on various metal-bearing aqueous solutions. (C) 2000 Elsevier Science B.V. All rights reserved.