ABSTRACT:A new type of interpenetrating polymer network (IPN) pervaporation membranes based on cellulose and synthetic polymers was developed. They were prepared by free-radical polymerization of acrylamide or acrylic acid in the presence (or absence) of the crosslinking agent (allyldextran or N,N-methylenebisacrylamide) within cellophane films swollen in the reaction mixture. The swelling behavior of these membranes in water-ethanol solutions and their separation characteristics were investigated depending on the polyacrylamide (PAAm) or poly(acrylic acid) (PAA) content in the IPN (C p ) and for ionic cellulose-PAA membranes depending on the degree of neutralization of carboxylic groups and on the type of counterions. IPN membranes were selective over a wide range of ethanol concentration in the feed. The separation factor ( a) and the permeation rate ( P) significantly improved with increasing C p in IPN membranes, especially for the cellulose-PAA(K / form) membranes (for 86% EtOH feed at 50ЊC, and a and P values reached 1500 and 1.6 kg/m 2 h, respectively). The results for ionic and nonionic IPN membranes were compared. The separation characteristics of membranes were in good correlation with their swelling behavior. The a values of the membranes depended on the affinity of the IPN polymer chains functional groups for water.

ABSTRACT:The separation properties in the dehydration of a water-ethanol mixture and the swelling behavior of interpenetrating polymer network (IPN) pervaporation membranes based on a cellulose or cellulose-hydroxyethyl cellulose (HEC) matrix and poly(acrylamide and/or acrylic acid) were investigated depending on the ionic acrylate groups content (␥) in synthetic polymer chains (0 -100 mol %), the HEC content in the matrix (0 -50 wt %), and the temperature (25-60°C). The separation factor (␣), permeation rate (P), and separation index (␣P) significantly improved with increasing ␥ values only for the separation of concentrated ethanol solutions (ϳ86 wt %). For more dilute solutions of ethanol (ϳ46 wt %), the P and ␣P values also increased but no considerable increase in ␣ was observed. All types of membranes based on the cellulose matrix were characterized by a drastic decrease in the values of P at [EtOH] Ն90 wt % and, as a result, a decrease in the separation index (kg m Ϫ2 h Ϫ1 ) from ϳ2000 (for 86 wt % EtOH, 50°C) to ϳ240 (for 95 wt % EtOH, 50°C), which correlates with a decrease in the degree of membrane swelling. The modification of the cellulose matrix by introducing HEC into it makes it possible to increase considerably the membrane swelling in concentrated EtOH solutions and, hence, the ␣P value to ϳ760 (95 wt % EtOH, 50°C). All types of IPN membranes exhibit a marked increase in both ␣ and P when the temperature increases from 25 to 60°C.