Block copolymer based nanocomposite membranes for Arsenic and Selenium removal from coal-fired powerplant wastewater

Abstract

The severity of risks caused by arsenic and selenium ions in aqueous environments are well-known. Novel thin film block copolymer based nanocomposite membranes are synthesized for an efficient removal of these toxic ions. Nexar, a commercially available amphiphilic sulfonated pentablock copolymer creates a self-ordering and a long range nano morphology. The resultant morphologies thus creating nano-highways helps in improving the flux through the resultant membranes. The effect of fouling in the membranes are countered by using octaphenyl-POSS as the nanofiller. The second phase of work aims at surface modification of Polyether imide nanofiltration membranes with enhanced separation for arsenic and selenium. Specifically, a zwitterionic copolymer comprising MPC and AEMA is synthesized via a one-pot free-radical polymerization. Different amounts of MPC and AEMA monomers were introduced at molar ratios of 5:5, 7:3, and 9:1 to tune the physicochemical properties of the newly developed copolymer and the effect on the filtration performance of these varied molar ratios of the monomers is kept under check. Comparative analysis was done based on results obtained from both works. Membranes modified with zwitterionic materials imparted their hydrophilic properties to the membranes with the WCA as low as 22o were observed for copolymers with molar ratio 7:3(MPC: AEMA). Whereas for the Nexar membranes with POSS incorporated the WCA were not as low. Based on the rejections, the membranes were also compared with the copolymeric membranes modified with water and TEA showing superior results than its counterpart as well as those with POSS incorporated Nexar membranes with rejection of 99.49% and 98.78% for arsenic and selenium respectively