Sustainable fabrication of zwitterionic nanofiltration membranes with enhanced antifouling performance using sugar

Thin-film composite membranes are vastly utilized to treat wastewater due to their high energy efficiency, low investment and environmental benignity. However, the use of hazardous solvents and non-renewable resources during membrane preparation poses a major threat to human health and the environment. Several tough challenges such as the trade-off effect between permeability and rejection as well as fouling require immediate remediation. To address these issues, this work integrated a green solvent and a bio-monomer, fructose in the membrane substrate and selective layer, respectively. The membrane is fabricated via facile interfacial polymerization with the addition of a zwitterionic monomer, 1-(2-hydroxyethyl) piperazine propane sulfonate (HEPPS) to promote antifouling properties. FTIR and XPS results depicted the formation of a polyesteramide membrane and the incorporation of zwitterion while AFM and FESEM micrographs showed the changes in membrane roughness. The synergistic effect of fructose and HEPPS in the selective layer increased water permeability from 3.54 to 4.77 L m⁻² h⁻¹ bar⁻¹ while having a remarkable Na₂SO₄ rejection of 99.1 %. Additionally, the zwitterionic membrane exhibited superior antifouling properties with a flux recovery ratio of 97.7 % and 93.4 % for bovine serum albumin and lysozyme, respectively. The results suggested that HEPPS and fructose could ameliorate the fouling resistance of the membrane significantly owing to their exceptional hydrophilicity. Moreover, the resultant membrane shows a stable chlorine resistance towards a high concentration of chlorine (10,000 ppm·h). The findings are expected to provide insights in designing membranes with improved antifouling properties and excellent separation performance coupled with green and sustainable fabrication.