Hydrophobic pervaporation of binary and ternary solutions: Evaluation of fluxes, selectivities, and coupling effects

In hydrophobic pervaporation, the evaluation and prediction of coupling effects in multicomponent systems is one of the key requirements to improve its applicability in the biotechnology and food industry. The focus of this study is first on binary aqueous systems with methanol, ethanol, acetone, 1-propanol, 2-propanol 1,3-dioxane, and 1,4-dioxane, and then on ternary aqueous systems with 1-propanol and a second organic/aromatic component. The pervaporation experiments were carried out with polydimethyl siloxane (PDMS)-zeolite Pervap 1070 membranes. From the binary experiments, it was found that for a homologous series of alcohols, flux and selectivity are increasing with liquid molar volume and activity coefficients. Dipole moments were identified as additional parameters to consider in the case of isomers. The experiments with ternary aqueous solutions revealed that the effect of coupling increases with the organic concentration. Furthermore, by introducing a coupling factor as a ratio of ternary and binary component permeability, it was found that the effect of coupling increases with decreasing molecular weight and reaches a maximum at the equimolar point of first and second organic components in the feed. This trend was similar for all organic/aromatic components considered in this study and gained further confirmation by using literature values.