Synthesis, characterization and desalination study of polyvinyl chloride-co-vinyl acetate/cellulose acetate membranes integrated with surface modified zeolites

Novel mixed matrix membranes of polyvinyl chloride-co-vinyl acetate/cellulose acetate (PVCA/CA) infused with nano-particles of both pristine zeolite (p-zeolite) and 3-aminopropyl triethoxysilane (APTS) functionalized zeolite (f-zeolite) were synthesized by dissolution casting method for desalination application. MMMs were then characterized using FTIR, SEM, contact angle and DMA analysis. FTIR and TGA analysis were also carried out for zeolite particles to confirm the surface functionalization. The loading effect of zeolite (1, 3 and 5 wt. %) and the impact of APTS functionalization on dispersion, morphological structure, thermo-mechanical properties and hydmphilicity were also analyzed. Desalination performance of the membranes was evaluated using 2000 ppm NaCl solution at 6 bar pressure. SEM analysis demonstrated that APTS functionalization improved the uniformity of the zeolite nano-particles in the membrane and a noticeable reduction in undesirable microscopic voids. Higher hydmphilicity was attained with the inclusion of f-zeolite nanoparticles, as confirmed by contact angle measurement analysis. It was found that the membrane infused with 5 wt. % of f-zeolite exhibited substantial improvements in storage modulus, glass transition temperature and cross-link density. Membranes infused with f-zeolite demonstrated enhanced transport mechanism without showing trade-off between water flux and salt rejection. In particular, inclusion of 5 wt. % f-zeolite, resulted in achieving the highest salt rejection of 99.56% with water flux increment of -24% in comparison to the neat PVCA/CA membrane. Finally, the membranes were tested for anti-fouling properties using flux recovery ratio test. Thus, the newly developed PVCA/CA membranes embedded with APTS f-zeolite can be exploited for high performance desalination applications.