Novel two-ply composite membranes of chitosan and sodium alginate for the pervaporation dehydration of isopropanol and ethanol

Novel two-ply dense composite membranes were prepared using successive cast ings of sodium alginate and chitosan solutions for the pervaporation dehydr ation of isopropanol and ethanol. Preparation and operating parameters name ly polymer types facing to the feed stream, NaOH treatment for the regenera tion of chitosan, and crosslinking system types were investigated using the factorial design method. It was shown that these parameters were all criti cal to the performance of the membrane in the form of the main and interact ion effects. The pervaporation performance of the two-ply membrane with its sodium alginate layer facing the feed side and crosslinked or insolubilize d in sulfuric acid solution was compared with the pure sodium alginate and the chitosan membranes in terms of the flux and separation factors. It was shown that although its flux was lower than that of the pure sodium alginat e and chitosan membranes, the separation factors at various alcohol concent rations were in between values for the two pure membranes. For the dehydrat ion of 90 wt% isopropanol-water mixtures the performance of the two-ply mem brane which was moderately crosslinked in formaldehyde was found to match t he high performance of the pure sodium alginate membrane. This two-ply memb rane had fluxes of 70 g/m(2) h at 95% EtOH, 554 g/m(2) h at 90% PrOH and se paration factors of 1110 at 95% EtOH, 2010 at 90% PrOH and its mechanical p roperties were better than that of the pure sodium alginate membrane. (C) 1 999 Elsevier Science B.V. All rights reserved.