Description of binary liquid mixtures transport through non-porous membrane by modified Maxwell–Stefan equations

This paper deals with a description of transport parameters during pervaporation of binary liquid mixture through non-porous polymer membrane. The main task of this work is the application of the model that would be able to describe the transport of the penetrant in the membrane. The influence of the C-number of aliphatic alcohols on transport parameters is also under study. The concentration dependent density of the membrane, vapor sorption isotherms, the dependence of pure component diffusion coefficients on their concentration in the membrane and the dependence of the solubility of liquid binary mixture in a membrane was necessary to determine experimentally. All mention dependencies were mathematically described and then introduced into modified Maxwell–Stefan equations. The model was used for the liquid binary mixtures (ethanol, propan-1-ol, butan-1-ol with toluene) and the low-density polyethylene membrane at 25 °C. Pervaporation data for all the three systems were measured in order to calculate coupled diffusion coefficient and to compare the model with the experiment. The dependencies of pervaporation fluxes and weight fraction of preferable penetrant in permeate on concentration of preferable penetrant in the feed are compared with the calculations based on the first Fick’s law with constant diffusion coefficient and modified Maxwell–Stefan equations.