Sorption, diffusion, and pervaporation separation of water-acetic acid mixtures through the blend membranes of sodium alginate and guar gum-grafted-polyacrylamide

Nonporous homogeneous dense membranes were prepared from the blends of sodi um alginate (Na-Alg) with guar gum-grafted polyacrylamide (GG-g-PAAm) in th e ratios of 3:1 and 1:1 and these were tested for the pervaporation separat ion of water-acetic acid mixtures at 30 degreesC. Blend compatibility was s tudied in solution by measuring the viscosity and the speed of sound. Membr anes were crosslinked by glutaraldehyde, The GG-g-PAAm polymer and the cros slinked blend membranes were characterized by Fourier transform infrared sp ectra. High separation selectivity was exhibited by the pure Na-Alg membran e for water-acetic acid (HAc) mixtures containing 20 mass % of water. The p ermeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG-g-PAAm in the blend, but se paration selectivity decreased. Sorption selectivity was higher for the Na- Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG-g-PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of wate r in the feed. Diffusion coefficients of the water-HAc mixtures were calcul ated from Fick's equation using sorption data and compared with those calcu lated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the fe ed using flux and diffusion data obtained at 30, 40, and 50 degreesC. The d iffusion and pervaporation results are explained in terms of solution-diffu sion concepts. (C) 2002 John Wiley & Sons, Inc.