Blend membranes of chitosan and poly(vinyl alcohol) in pervaporation dehydration of isopropanol and tetrahydrofuran

Blend membranes of a natural polymer, chitosan, with a synthetic polymer, poly(vinyl alcohol) (PVA), were prepared by solution casting and crosslinked with a urea formaldehyde/sulfuric acid (UFS) mixture. Chitosan was used as the base component in the blend system, whereas PVA concentration was varied from 20 to 60 wt %. Blend compatibility was studied by differential scanning calorimetry, and Fourier transform infrared spectroscopy was used to study membrane crosslinking. Membranes were tested for pervaporation dehydration of isopropanol and tetrahydrofuran (THF) at 30 degrees C in close proximity to their azeotropic compositions. Membrane performance was assessed by calculating flux and selectivity. Swelling experiments per-formed in water + organic mixtures at 30 C were used to explain the pervaporation results. The blend membrane containing 20 wt % PVA when tested for 5 and 10 wt % water-containing THF and isopropanol feeds exhibited selectivity of 4203 and 17,991, respectively. Flux increased with increasing concentration of water in the feed. Selectivity was highest for the 20 wt % PVA-containing blend membrane. The results of this study are unique in the sense that the cross-linking agent used-the UFS mixture-was novel. (c) 2006 Wiley Periodicals, Inc.