QUANTITATIVE APPROACH FOR THE PREDICTION OF PREFERENTIAL SORPTION IN THE CASE OF PERVAPORATION OF A PHYSICOCHEMICALLY SIMILAR BINARY MIXTURE

Selective transport by pervaporation of physico-chemically similar and polar components through a polar membrane is complicated due to compe titive sorption and diffusion phenomena. In the present study the mech anism of preferential sorption has been predicted for such a system, m ethanol-ethylene glycol-cellophane. The mechanism has been explained i n terms of intercrystalline swelling of the polymer matrix in presence of increasing methanol concentration in the feed. The reduction in pr eferential sorption at increasing wt% of methanol in the feed may be d ue to the increasing accessibility of the membrane towards ethylene gl ycol. This phenomenon has been quantitatively explained by considering a non-linear dependence on concentration of the binary liquid-polymer interaction parameter. Theoretical sorption data have been derived fr om the Flory-Huggins thermodynamics by using the swelling equilibrium condition. The coupling and plasticization phenomena in sorption are e xplained in terms of liquid-polymer interaction parameters. The theore tical results show good agreement with previously published experiment al data.