Enhancing selectivity of nanofiltration membranes for mineral ions and per- and polyfluoroalkyl substances via dual-component-assisted interfacial polymerization.

Highly negatively charged nanofiltration membranes with tailored pore sizes can effectively reject trace per- and polyfluoroalkyl substances (PFAS) while allowing the passage of beneficial mineral ions, making them ideal for advanced drinking water purification. This study proposed a novel dual-component-assisted interfacial polymerization (IP) strategy aiming at enhancing membrane selectivity between PFAS and mineral ions. The step-wise involvement of p-Phenylenediamine as the aqueous co-monomer and 1,3,5-triformyl phloroglucinol as the pre-loading organic phase properly tailored the IP kinetics for polyamide layer formation. This strategy achieved superior effect compared to others adopting single component or mixed organic phase, yielding high-performance membranes characterized by looser structures, higher negative charge density, thinner thickness, and enhanced hydrophilicity. The optimal membrane demonstrated a high water permeance of 20.4 L m h bar, over 88 % rejections for six kinds of PFAS (300-514 Da), and a Ca/PFAS selectivity exceeding 37 when treating practical tap water, surpassing numerous commercial and previously developed membranes. Furthermore, the novel membrane exhibited excellent long-term stability and improved resistance to organic fouling and gypsum scaling. This study presents a promising solution of nanofiltration for drinking water treatment requiring efficient removal of trace PFAS and high preservation of mineral ions.