Kinetic modelling of the active transport of copper(II) across liquid membranes using thiourea derivatives immobilized on microporous hydrophobic supports

Abstract

The facilitated transport of Cu^II from chloride media through a flat-sheet supported liquid membrane (FSSLM) is investigated, using thiourea derivatives as ionophores, as a function of hydrodynamic conditions, concentration of copper (1–3×10^-7 mol cm^-3) and H⁺ (pH 0.1–2.5) in the feed solution, structure of carrier, carrier concentration (0.7–3×10^-5 mol cm^-3) in the membrane, strippant in receiving phase and support characteristics. A model is presented that describes the transport mechanism, consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion of carrier and its metal complex through the organic membrane. The organic membrane diffusional resistance (Δ_o) and aqueous diffusional resistance (Δ_a) were calculated from the proposed model, and their values were 107×10² s cm^-1 and 625 s cm^-1, respectively. It was observed that the Cu^II flux across the membrane tends to reach a plateau at a high concentration of Cu^II or a low concentration of H⁺ owing to carrier saturation within the membrane, leading to a diffusion-controlled process. The values of the apparent diffusion coefficient (D_o^a) and limiting metal flux J_lim were calculated from the limiting conditions and found to be 2.9×10^-6 cm² s^-1 and 1.4×10^-9 mol cm^-2 s^-1, respectively. The values of the bulk diffusion coefficient (D_o,b) and diffusion coefficient (D_o) calculated from the model were 2.6×10^-6 cm² s^-1 and 1.2×10^-6 cm² s^-1. The polymeric microporous solid support, Durapure, was selected throughout the study as it gave the best performance.