SORPTION OF ALCOHOL-TOLUENE MIXTURES IN POLY(ACRYLIC ACID)-POLY(VINYLALCOHOL) BLEND MEMBRANES AND ITS ROLE ON PERVAPORATION

The overall and preferential sorption of alcohol-toluene mixtures in h omogeneous blends of poly(acrylic acid) and poly(vinyl alcohol) were d etermined. Both the overall solubility and the equilibrium sorption se lectivity were strongly dependent on the composition of the blend and of the liquid feed mixture.,The swelling of the blends increased with increasing poly(acrylic acid) content and with increasing alcohol cont ent in the liquid mixtures. Alcohols were sorbed preferentially over t oluene in all cases tested. The equilibrium sorption selectivity incre ased with increasing poly(vinyl alcohol) content in the blends and wit h decreasing alcohol content in the liquid mixtures. The equilibrium s orption selectivity was predicted by a model which was derived from Fl ory-Huggins thermodynamics. The agreement between the predicted and th e experimental results was very good. In addition, the equilibrium sor ption results were compared with the pervaporation results, and this c learly shows that preferential sorption dominates the pervaporation se lectivity in the systems studied.