Coupled effect of the membrane properties and concentration polarization in pervaporation: Unified mass transport model

The effect of the concentration boundary layer on the membrane separation is well known and intensively discussed in the literature. In most of these studies, the effect of the membrane layer on the separation is missing. Recently, some papers have been published which take into account both the concentration polarization layer and the membrane layer on the membrane separation by means of pervaporation. These papers use mostly the resistance-in-series model and try to incorporate the effect of the boundary layer's Peclet number, as well. These models do not make possible the direct calculation of the separation characteristics, e.g. the enrichment or the polarization modulus. A coupled model of concentration polarization and diffusion transport through the membrane was developed which enables the direct prediction of the concentration distribution in both layers and other important separation properties as enrichment, polarization modulus, etc. The calculated data are compared with the experimental ones taken from the literature. The excellent agreement between the measured and predicted data proves that the equations developed are suitable to describe the pervaporation process or to predict its effectiveness. It has also been demonstrated the strong effect of the membrane properties on the concentration distribution of both layers and on the mass transfer rate, consequently on the separation efficiency.