Sorption of Alcohol−Toluene Mixtures in Poly(acrylic acid)−Poly(vinyl alcohol) Blend Membranes and Its Role on Pervaporation

Abstract

The overall and preferential sorption of alcohol-toluene mixtures in homogeneous blends of poly(acrylic acid) and poly(vinyl alcohol) were determined. Both the overall solubility and the equilibrium sorption selectivity 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 content in the liquid mixtures. Alcohols were sorbed preferentially over toluene in all cases tested. The equilibrium sorption selectivity increased with increasing poly(vinyl alcohol) content in the blends and with decreasing alcohol content in the liquid mixtures. The equilibrium sorption selectivity was predicted by a model which was derived from Flory-Huggins thermodynamics. The agreement between the predicted and the experimental results was very good. In addition, the equilibrium sorption results were compared with the pervaporation results, and this clearly shows that preferential sorption dominates the pervaporation selectivity in the systems studied.