Modelling of nickel permeation through a supported liquid membrane

This paper presents a mathematical model for the permeation of nickel(II) ions from sulfate solutions through supported liquid membranes (SLM) which contain di(2-ethylhexyl) phosphoric acid (D2EHPA) as the carrier, dissolved in kerosene. This process of facilitated transport, based on membrane technology, is a variation on the conventional technique of solvent extraction and may be described mathematically using Pick's second law. The equations for permeation velocity are derived considering the diffusion of D2EHPA and its metallic complexes through the liquid membrane. In this work, the system is considered to be in a transient state, and chemical reaction between nickel and the carrier to take place only at the solvent-aqueous interfaces. Model concentration profiles are obtained for the nickel ions, from which extraction velocities are predicted. The experimental and simulated nickel extractions showed similar tendencies for a high nickel concentration, neutralized case. The model results indicate that high initial nickel concentrations and large membrane thicknesses both have detrimental effects on nickel extraction and stripping.