Analysis of sorption and permeation of acetic acid-water mixtures through unfilled and filled blend membranes

A systematic method was employed for making blend membranes from two different hydrophilic polymers. Accordingly, blend membranes of polyvinyl alcohol (PVA) and sodium carboxy methyl cellulose (CMC) at three different wt ratio i.e. PVA:CMC wt ratio of 1:0.25, 1:0.5 and 1:0.75 were prepared. These blend membranes were designated as PC1, PC2 and PC3, respectively. Each of these membranes was crosslinked with 2 wt% (of total polymer) maleic acid. These membranes were used for pervaporative (PV) separation of acetic acid-water mixtures at different feed compositions and temperatures. PC2 membrane showing optimum flux and water selectivity was further filled with 1, 2 and 3 wt% (of total polymer) hydrophilic bentonite filler to produce three different filled membranes i.e. B1PC2, B2PC2 and B3PC2, respectively. These filled membranes were also used for separation of acetic acid-water mixtures. Both unfilled and filled membranes were characterized by FT-IR and UV spectroscopy, SEM, XRD, DSC and mechanical properties. Sorption of the membranes was analyzed by Flory-Huggins thermodynamics. Partial permeability of water and acid through the membranes were determined. Diffusion coefficient of permeants was also determined using a model based on free volume theory. Among these six membranes B2 PC2 membrane showed optimum performance in terms of flux and selectivity.