Enhanced trace organic compounds removal in nanofiltration via secondary interfacial polymerization: mechanistic insights and performance prediction

Trace organic compounds (TrOCs) in aquatic environments pose risks to human health and ecosystems, necessitating the development of high-performance nanofiltration (NF) membranes. While secondary interfacial polymerization (SIP) offers a promising approach for membrane modification, the mechanistic understanding of how specific functional groups introduced by SIP govern the rejection of TrOCs with diverse properties remains limited, impeding the design of membranes for targeted removal. A series of dual-layer NF membranes via SIP were prepared, introducing three hydrophilic functional groups (-SO 3 H, -OH, -NH 2 ) to tailor membrane properties. -NH 2 -modified membrane exhibited the smallest pore size and a highly cross-linked structure, leading to the highest rejection (> 85 %) of TrOCs via steric exclusion. -SO 3 H-modified membrane demonstrated strong electronegativity, which enhanced the negatively charged TrOCs removal through electrostatic repulsion. -OH-modified membrane, with its enlarged pore structure and moderate hydrophilicity, showed the highest water permeability but lower TrOCs rejection. Donnan steric pore model (DSPM) accurately predicted the rejection of hydrophilic and charged TrOCs, while a correction factor accounting for hydrophobic interactions was essential for modeling hydrophobic compounds. Membrane thickness showed negligible influence under the tested conditions. This work provides mechanistic insights and a predictive framework for designing NF membranes with customized properties for TrOCs removal.