EFFECTS OF FEED-SIDE SOLUTE POLARIZATION ON PERVAPORATIVE STRIPPING OF VOLATILE ORGANIC SOLUTES FROM DILUTE AQUEOUS-SOLUTION - A GENERALIZED ANALYTICAL TREATMENT

A simplified analytical model of solute and solvent transport for a di lute solution of a sparingly soluble volatile organic compound in aque ous solution during pervaporation through a solute-permselective membr ane graphically demonstrates the importance of feed-side boundary laye r resistance on the overall selectivity and capacity of the separation process. Nomographs allowing prediction of operating performance char acteristics for pervaporation (e.g., enrichment ratio, process selecti vity, and solute permeation flux) from a knowledge of a small number o f readily-accessible thermodynamic and physicochemical properties of t he liquid-phase components and membrane, and of feed-side hydrodynamic parameters, are presented. The analysis reveals that, even under the most favorable conditions for minimizing feed-side polarization, perva porative separation of components in such systems is severely compromi sed by feed-side boundary layer transport resistance. Operating condit ions needed to optimize pervaporative performance are proposed. It is suggested that, for such systems, a hybrid process comprising staged l iquid/liquid extraction in combination with liquid/liquid separation b y crossflow microfitration may be a more practical and economic approa ch to this important problem.