Kinetics of the Transport of Co(II) from Aqueous Sulfate Solution through a Supported Liquid Membrane Containing Di(2-ethylhexyl) Phosphoric Acid in Kerosene

Abstract

The permeation rate of Co²⁺ from its aqueous sulfate solution through a solid supported liquid membrane containing di(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene as mobile carrier has been studied as a function of hydrodynamic conditions, concentrations of Co²⁺ (0.17−4.25 mol/m³) and H⁺ (pH 3.5−6.0) in the feed solution, carrier concentration (20–400 mol/m³) in the membrane, and temperature. It has been observed that Co²⁺ flux across the membrane tends to reach a plateau region at a higher concentration of Co(II) or a lower concentration of H⁺ due to carrier saturation within the membrane, leading to a diffusion-controlled process. It is also observed that Co²⁺ flux is about second order with respect to dimerized carrier at a lower D2EHPA concentration (≶150 mol/m³) and exhibits a lower order (0.6–1.0) at a higher concentration of D2EHPA. Necessary kinetic parameters have been derived from the model equations based on the combination of aqueous film diffusion, interfacial chemical reaction, and membrane diffusion. The low activation energy value suggests that the process is predominantly diffusion controlled.