Journal of Membrane Science & Technology

Abstract

Nonequilibrium Dissolution-diffusion Model for PDMS Membrane Pervaporation of ABE Water Binary System

Xia Yang, Zhen Wu, Fang Manquan and Li Jiding

Previous models of equilibrium dissolution-diffusion, pore flow and virtual phase change cannot describe the mass transfer process of pervaporation precisely. The fact that dissolution process on the surface of the membrane does not reach equilibrium is seldom emphasized in the literature. The aim of the present work is to develop the nonequilibrium dissolution-diffusion model (nonequilibrium model) for membrane pervaporation process. In this research, the steps of dissolution and desorption were treated as the pseudo surface reaction processes on the surface based on the hypothesis of nonequilibrium dissolution at the interface of the feed liquid and membrane. The semi-experimental model was set based on steady state mass transfer, ignoring the concentration polarization and adsorption at the permeation side. Through linear fitting of the flux with different thickness of the membrane, the diffusion coefficients and adsorption kinetic rate constants of the model were achieved with equilibrium partition coefficient estimated by UNIFAC-ZM model. The calculated values of the model were well in consistent with experimental flux in the vacuum pervaporation of acetone, butanol and ethanol with polydimethylsiloxane membrane. The nonequilibrium model and its parameters will be further applied for prediction of separation performance and selection of operation conditions.