Modelling of zinc extraction from sulphate solutions with bis(2-ethylhexyl)thiophosphoric acid by emulsion liquid membranes

This study reports the modelling of zinc extraction from sulphate media with bis(2-ethylhexyl)thiophosphoric acid by emulsion liquid membranes. The model developed by Lorbach et al. [Ger. Chem. Eng. 9 (5) (1986) 321] was extended to the present situation. The model accounts for the chemical reactions between the Zn2+ ions and the carrier molecules and transient diffusion of solutes within the emulsion globule. The speciation of the sulphate acidic aqueous solutions was included in the model to predict the concentration of the proton during permeation. The activity coefficients were calculated by applying the Pitzer model. The reaction rate constants of zinc extraction were also calculated by taking into account the non-ideality of the aqueous phase. The batch extraction of zinc was carried out under various experimental conditions. The agreement between the calculated results and the experimental data was found satisfactory, mainly for a reduced permeation time. (C) 2004 Elsevier B.V. All rights reserved.