Sodium citrate-modulated interfacial polymerization towards highly permeable NF membranes for simultaneously enhanced mineral/NOM selectivity and anti-fouling performance

The elimination of natural organic matter (NOM) and organic micropollutants, while effectively preserving essential dietary minerals, constitutes a crucial objective during nanofiltration (NF) of healthy drinking water production. In this study, sodium citrate (SC), distinguished by its unique functional group, was selected as an aqueous phase additive to customize interfacial polymerization for multifunctional NF membranes. The resultant NF membranes exhibited optimal pore sizes, enhanced negative charge density, increased hydrophilicity, and improved separation selectivity. The optimized NF membrane (PIP-SC6) demonstrated a water permeance of 27.8 LMH bar⁻¹ and achieved over 80 % NOM removal while maintaining calcium and magnesium retention below 10 %. Impressively, PIP-SC6 displayed >76.9 % rejection for four selected organic micropollutants while achieving double the permeance compared to commercial NF270. The effluent produced showed low levels of organic matter content while retaining beneficial mineral elements suitable for healthy drinking water consumption. Furthermore, PIP-SC6 exhibited double resistance to both organic fouling and gypsum fouling compared to NF270. This research offers a new approach to customizing highly selective NF membranes aimed at producing healthy drinking water.