PVA modified filled copolymer membranes for pervaporative dehydration of acetic acid-systematic optimization of synthesis and process parameters with response surface methodology

The separation potential of acrylic copolymer membrane was significantly improved by modifying it with polyvinyl alcohol (PVA) and nano sized sodium montmorillonite (NaMMT) clay. Accordingly, several membranes were prepared from the polymers synthesized by emulsion polymerization of acrylonitrile (AN) and acrylic acid (AA)in the presence of varied concentrations of PVA and NaMMT clay in the reaction mixtures. The synthesis parameters, i.e., comonomer ratios, wt% of PVA and wt% of clay were optimized by three level factorial design of response surface methodology (RSM) with respect to flux and separation factor for 90 wt% acetic acid in water. The membrane prepared with optimized synthesis parameters, viz., with AN: AA molar ratio of 5:1, PVA and clay of 5 wt% each (of total monomer wt.) was further subjected to dehydration of acetic acid at varied process conditions, i.e., feed concentration, temperature and downstream pressures. The process parameters were also optimized with similar RSM. The optimized membrane showed long time stability with high flux and separation factor, i.e., 0.520 kg/m2h and 203, respectively for 90 wt% acid in water at 30 °C and 1.5 kPa downstream pressure.