Facilitated transport of lead(II) and cadmium(II) through novel activated composite membranes containing di-(2-ethyl-hexyl)phosphoric acid as carrier

This paper describes an approach to the chemical characterisation of the facilitated transport of lead(II) and cadmium(II) by an activated composite membrane (ACM) containing immobilised di-(2-ethyl-hexyl)phosphoric acid (DEHPA). Such membranes were prepared, by interfacial polymerisation and characterised physically and chemically. The ACMs were used to experimentally determine their transport behaviour for Pb(II) and Cd(II). So, the influence of some chemical parameters (i.e. DEHPA concentration on the ACM, the feed solution composition, the concentration of nitric acid in the stripping solution, and the ionic strength of the feed and stripping aqueous solutions) was assayed for each metal ion. A correlation of the chemical behaviour of those ACM systems with the physical characterisation of those membranes, prior to and after their use, is reported. The optimum chemical conditions for Pb(II) and Cd(II) transport enhance the lifetime of the ACMs, giving higher DEHPA immobilisation on the polymeric phase of the composite membrane. (C) 2000 Elsevier Science B.V. All rights reserved.