Pervaporation of isopropanol-water mixtures through polyion complex membranes

Polyion complex membranes made by blending 84% deacetylated chitosan and poly(acrylic acid) were tested for the separation of isopropanol-water mixtures. The membranes were characterized by FT-IR to verify the formation of the polyion complex, XRD to observe the effects of blending on crystallinity, DSC 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 polyion membranes, in pure as well as mixtures of the two liquids. Amongst the blends tested, the crosslinked membranes having 60 wt.% of chitosan were found to have good potential for breaking the aqueous azeotrope of 87.5 wt.% of Isopropanol yielding a high selectivity of 1736 at a reasonable flux of 0.14 kg/m2 h 10 μm. Membrane selectivities were found to improve with decreasing permeate pressure but remained relatively constant for variable membrane thickness. Increasing membrane thickness decreased the flux and higher permeate pressure caused a fall in membrane performance.