Copper separation from nitrate/nitric acid media using Acorga M5640 extractant: Part II. Supported liquid membrane study

Abstract

The facilitated transport of copper(II) from nitrate/nitric acid media through a flat-sheet supported liquid membrane (FSSLM) is investigated, using the commercially available oxime Acorga M5640 as ionophore, as a function of hydrodynamic conditions, concentration of copper (7.9×10 −5 to 1.3×10 −3 M) and H + (pH 1.0–2.0) and ionic strength in the feed solution, carrier concentration (5–40% v/v) in the membrane and support characteristics. The performance of the system is also compared using various diluents for the organic phase and against other available oxime extractants (MOC-55TD, LIX 860 and LIX 622). A model is presented that describes the transport mechanism, consisting of diffusion through a feed side 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 7.6×10 6 and 273 s/cm, respectively. It was observed that the copper flux across the membrane tends to reach a plateau at high concentration of copper or a low concentration of H + owing to carrier saturation within the membrane, and leads 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 2.0×10 −8 cm 2/s and 2.3×10 −11 mol/cm 2 s, respectively. The values of the bulk diffusion coefficient ( D o,b) and diffusion coefficient ( D o) calculated from the model were 5.9×10 −9 and 1.6×10 −9 cm 2/s, respectively. The polymeric microporous solid support, Durapore GVHP 04700, was selected throughout the study as it gave the best performance.