High-Performance\nNanofiltration Membrane with Dual\nResistance to Gypsum Scaling and Biofouling for Enhanced Water Purification

Nanofiltration (NF) technology is\npivotal for ensuring\na sustainable\nand reliable supply of clean water. To address the critical need for\nadvanced thin-film composite (TFC) polyamide (PA) membranes with exceptional\npermselectivity and fouling resistance for emerging contaminant purification,\nwe introduce a novel high-performance NF membrane. This membrane features\na selective polypiperazine (PIP) layer functionalized with amino-containing\nquaternary ammonium compounds (QACs) through an <i>in situ</i> interfacial polycondensation reaction. Our investigation demonstrated\nthat precise QAC functionalization enabled the construction of the\nselective PA layer with increased surface area, enhanced microporosity,\nstronger electronegativity, and reduced thickness compared to the\ncontrol PIP membrane. As a result, the QAC NF membrane exhibited an\napproximately 51% increase in water permeance compared to the control\nPIP membrane, while achieving superior retention capabilities for\ndivalent salts (>99%) and emerging organic contaminants (>90%).\nFurthermore,\nthe incorporation of QACs into the PIP selective layer was proved\nto be effective in mitigating mineral scaling by allowing selective\npassage of scale-forming cations, while simultaneously exhibiting\nstrong antimicrobial properties to combat biofouling. The <i>in situ</i> QAC incorporation strategy presented in this study\nprovides valuable guidelines for the fit-for-purpose design of the\nselective PA layer, which is crucial for the development of high-performance\nNF membranes for efficient water purification.