Sorption equilibria and diffusion in polymeric membranes

• Published in: Fluid phase equilibria 1989, Vol.51, p.369-381
• Main Authors: Hauser, J., Heintz, A., Schmittecker, B., Lichtenthaler, R.N.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-gas interface; Surface physical chemistry
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/0378-3812(89)80377-2

Results are reported of static and dynamic vapor-sorption experiments of H 2O, CH 3OH, C 2H 5OH and 1-C 3H 7OH in synthetic membranes made of poly-vinylalcohol (PVA) and poly-etherimide (PEI). The sorption process is faster at higher temperatures, however, in the range investigated the total amount absorbed at saturation is practically independent of temperature. Diffusion coefficients of pure substances have been determined from studying the sorption process as a function of time. Absorption of vapor mixtures of H 2O + CH 3OH and H 2O + C 2H 5OH in PVA shows non-additivity with respect to the solubilities of the pure components, clearly revealing the mutual influence of the various components present in the membrane polymer. In addition swelling experiments have been performed for the PVA-membrane in the liquid and corresponding equilibrium vapor phases of H 2O + CH 3OH, + C 2H 5OH, + 2-propanol and + 1,4-dioxane respectively. The results clearly show, that an extrapolation of solubility data determined with non-saturated vapors to saturation conditions, i.e. to conditions where the sorption from a vapor phase equals that one from the corresponding equilibrium liquid phase, may yield results far too small.