Studies on pervaporative characteristics of bacterial cellulose membrane

Cellulose membrane produced by bacterial Acetobacter xylinum was deproteinated and investigated for pervaporative separation of aqueous organic mixtures. The permeate flux, selectivity, pervaporation separation index (PSI), solubility and degree of sorption were studied as a function of increasing concentration of organics in the feed. The membrane was found highly selective to water; highest selectivity [αp = 186] was obtained for a mixture of trihydric alcohol viz. glycerol (Gly) with 40% (v/v) water. The binary system of monohydric alcohol viz. ethanol (EtOH) and water (40% (v/v)) showed the lowest selectivity [αp = 12] but the highest pervaporative flux of 614 gm−2 h−1 at 35 °C which further increased to 1429 gm−2 h−1 at 75 °C. However, selectivity decreased to 1.3 with the increase in temperature. The pervaporation behaviour was interpreted in terms of sorption and diffusivity of the organics, which in turn, was influenced by the extent of their hydrogen bonding with the cellulose units in the membrane and the plasticization induced by the permeating water present in the binary mixture. Substantially high pervaporative separation index (PSI) of the order of 103-104 gm−2 h−1 and comparatively lower energy of activation (Ej) of 10 kJ/mol is indicative of the pervaporative potential of the bacterial cellulose membrane (BCM) in the separation of aqueous binary mixtures.