MODELING OF THE PERVAPORATION SEPARATION OF ETHANOL WATER MIXTURES THROUGH CROSS-LINKED POLY(VINYL ALCOHOL) MEMBRANE

A mathematical model for the permeation of liquid mixtures through polymeric membranes taking into account the coupling of fluxes has been developed. The model is based on the extension of Fujita's free volume theory and Flory-Huggins thermodynamics and is applied to the pervaporation separation of the full range of ethanol-water mixtures through crosslinked poly(vinyl alcohol) (PVA). The model includes the diffusion coefficient of the individual penetrants and terms that explain the plasticization action of a penetrant and the coupling effect of the permeation through the membrane of one penetrant on permeation of the other penetrant. Diffusivity data having practical values for the pervaporation process were determined from steady-state pervaporation experiments of single components. Coupling parameters were also introduced to explain the coupling behavior and plasticization action of the penetrants. Comparisons were made between the simulated and calculated permeabilities obtained from the model and the experimental values, respectively.