A mass transfer model for the extraction of weak acids/based in emulsion liquid-membrane systems

Abstract

A mathematical model for analysing the extraction of weak acids and weak bases from aqueous solution by liquid surfactant membrane has been presented. The model assumes that the reactions are reversible and the reaction equilibrium to exist in both the internal phase and the external continuous phase. The scheme for mass transfer analysis is based on an immobilized emulsion globule drop model and the classical film theory, i.e. the overall mass transfer resistance includes that due to the external turbulent boundary layer, the interfacial surfactant layer and the diffusion layer within the emulsion globule. The leakage effect of internal phase due to membrane rupture is also discussed in the mathematical treatment. The proposed model predicts satisfactorily the experimental results of the extraction of weak acids as well as weak bases in a batch separation system as presented in the literature.