Dehydration of ethanol through blend membranes of chitosan and sodium alginate by pervaporation*1

Polyion complex membranes made by blending 84% deacetylated chitosan and sodium alginate biopolymers followed by crosslinking with glutaraldehyde were tested for the separation of ethanol–water mixtures. The membranes were characterized by FTIR to verify the formation of the polyion complex, X-ray diffraction (XRD) to observe the effects of blending on crystallinity, DSC, and TGA to investigate the thermal stability, and tensile testing to assess their mechanical stability. The effect of experimental parameters such as feed composition, membrane thickness and permeate pressure on separation performance of the crosslinked membranes was determined. Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the blend membranes, in pure as well as mixtures of the two liquids. Crosslinked blend membranes were found to have good potential for breaking the azeotrope of 0.135mol fraction of water and a high selectivity of 436 was observed at a reasonable flux of 0.22kg/(m210μmh). Membrane selectivities were found to improve with decreasing membrane pressure but remained relatively constant for variable membrane thickness. Increasing membrane thickness decreased the flux and higher permeate pressure caused a reduction in both flux and selectivity.