Tuning water transport channels in sulfonated copolymer membranes for highly effective removal of arsenic and selenium from industrial wastewater

The increasing presence of heavy metal such as arsenic and selenium in wastewater discharge has brought considerable attention to the advanced membrane technologies that can effectively remove these toxic metals on an industrial scale. The most pressing challenge is fabricating membranes capable of effective removal while maintaining high permeability and mechanical integrity. In this work, we engineered high-performance membranes using Nexar™, a commercially available sulfonated pentablock copolymer. We systematically optimized the membrane performance by varying solvent systems (isopropanol/toluene versus THF) and incorporation of octa-phenyl polyhedral oligomeric silsesquioxane (POSS) nanoparticles as an additive. The optimized membrane containing 0.5 wt% POSS in an isopropanol/toluene solvent system demonstrated exceptional performance, achieving a pure water permeability of 95 ± 0.4 LMH/bar. This improvement was more than 10-fold compared to the commercial thin-film nanocomposite membranes while maintaining outstanding rejection rates of 98.2 % for arsenic and 98.05 % for selenium ions. Comprehensive characterization through SEM, AFM, and EDX revealed that optimal POSS loading enhances membrane performance and mechanical properties, with tensile strength improvements up to 87.1 %. These findings highlight the potential of POSS-Nexar™ membranes offering a promising solution for industrial wastewater treatment applications.