An attempt has been made in this paper to overcome the shortcomings of the advancing front model while simplifying the mathematical treatment of mass transfer and reaction occurring in the emulsion globule during extraction by liquid surfactant membranes. This model combines the mathematical simplification achieved in assuming a reaction front in the emulsion globule along with the realistic assumption of reaction equilibrium existing in the internal and external continuous phases. The proposed model predicts satisfactorily the experimental results of the extraction of weak acids and weak bases in a batch separation system as presented in various literatures.