Isopropanol thermal treatment strategy for enhancing commercial nanofiltration membrane performance: High selectivity and superior antifouling capability

Commercial nanofiltration (NF) membranes face significant challenges including low permeate flux, membrane fouling, and difficulty in precisely tuning separation selectivity. This study presents an innovative isopropanol (IPA) thermal treatment strategy for optimizing commercial NF270 membrane performance. Through systematic characterization, we demonstrate that IPA molecules penetrate polyamide molecular chain interstices, weakening intermolecular interactions through solvation effects to achieve controllable crosslinking reduction from 60.4 % to 20.3 %. The de-crosslinking processes significantly improved surface hydrophilicity and enhanced surface negativity. The optimized NF-IPA/60 membrane exhibited high permeance (26.7 LMH/bar) and excellent Na 2 SO 4 rejection (>95.7 %) while achieving enhanced selectivity for monovalent species. When treating natural surface water, NF-IPA/60 demonstrated superior contaminant removal and mineral retention capabilities, achieving >80.2 % organic contaminant removal while allowing moderate passage of beneficial minerals (Ca 2+ , Mg 2+ ). Additionally, the membrane exhibited exceptional antifouling performance with flux recovery ratios exceeding 91.7 % throughout three fouling cycles, attributed to synergistic effects of enhanced surface charge, improved hydrophilicity, and reduced surface roughness. This approach provides a facile, environmentally friendly pathway for developing high-performance NF membranes with tailored separation characteristics for advanced water treatment applications.