Pervaporation separation of water-isopropyl alcohol mixtures with blend membranes of sodium alginate and poly (acrylamide)-grafted guar gum

The blend membranes of sodium alginate (Na-Alg) and poly(acrylamide)grafted guar gum (PAAm-g-GG) in the ratios of 3:1 and 1:1 were prepared and studied for the pervaporation separation of water-isopropyl alcohol mixtures over the entire range of mixture composition at 30 degreesC. Membranes prepared from neat Na-Alg (M-1) and the 1:1 blend of Na-Alg and PAAm-g-GG (M-3) showed the highest separation selectivity for 10 mass % water in the feed mixture, whereas membranes prepared with the 3:1 blend ratio of Na-Alg to PAAm-g-GG showed the highest separation selectivity of 20 mass % water in the feed. Selectivity decreased with increasing amount of water in the feed for all the membranes, but these values show an increase with increasing amount of grafted copolymer in the blend mixture. Flux increased with increasing amount of water in the mixture, but the flux values did not change markedly with the PAAm-g-GG content in the blend membrane at the lower mass % water. At higher mass % of water, the flux values of the blends increase systematically with increasing amount of PAAm-g-GG in the blend polymer. For the 10 mass %-containing binary mixtures, the pervaporation separation experiments were performed at 30, 40, and 50 degreesC, and the resulting data were used to calculate the Arrhenius activation parameters. These data indicated activated pore-type diffusion of the permeants in the membranes. Dynamic sorption studies were also performed on up to 40 mass % water-isopropyl alcohol mixtures at 30 degreesC. These results, when analyzed by the empirical equation, indicated Fickian transport in all the cases. (C) 2002 Wiley Periodicals, Inc.