Separation of NMP/water mixtures by nanocomposite PEBA membrane: Part I. Membrane synthesis, characterization and pervaporation performance

Novel composite poly(ether-block-amide) (PEBA-2533) membranes were prepared in 90:10 v/v ethanol-water mixed solvent system for pervaporation of n-methyl pyrrolidone (NMP)/water mixtures. Hydrophilic 4A zeolite was incorporated to the extent of 10-40% of polymer weight to enhance separation properties. The synthesized membranes were crosslinked with 2% v/v 2, 4-toluylene-diisocyanate (TDI) in hexane medium for 4 h to reduce degree of swelling and improve selective nature with respect to water. Sorption studies were carried out in pure water, NMP and binary mixtures of varying compositions to establish membrane-liquid interactions. Membranes were characterized by FTIR, XRD and SEM to study formation of new functional groups and intermolecular interactions, degree of crystallinity and d-spacing, besides morphologies of surface and cross-section of the composite films, respectively. Effect of feed composition on membrane performance was evaluated using the optimum 30% zeolite-loaded membrane. For a feed mixture containing 2.87 wt.% water, a selectivity of 122 at a reasonable flux of 55 g/m2h was observed. PEBA-2533 membrane appears to have considerable potential for dewatering of highly polar aprotic solvents owing to its ability to dehydrate NMP to purity levels of > 99%. The composite nature of the membrane makes it feasible to fabricate modular configurations for scale-up.