Computational simulation was conducted to predict mass-transfer phenomenon in the molecular separation of solute using microporous membrane contactors. Both diffusional and convectional mass-transfer mechanisms were considered. The membrane system was a hollow-fiber contactor in which an aqueous phase containing an organic compound was contacted with an organic phase for extractive separation of the solute. Benzoic acid was used as the solute. The main focus was on understanding the mass transfer of solute in the process. The concentration equation for the solute was solved numerically using a computational fluid dynamics approach. It was found that the model can predict the solute transport from the aqueous phase to the organic phase and can be used as a predictive model for process understanding.