Scalable catalytic nanofiltration membranes for advanced water treatment

Abstract

Commercial nanofiltration and reverse osmosis membranes are inherently inefficient at removing small, neutral organic contaminants. In this study, we biomimetically designed a catalytic nanofiltration membrane that synergizes advanced oxidation with nanofiltration to achieve near-complete removal of contaminants, ranging from salts to small organic contaminants, addressing a key deficiency of nanofiltration and reverse osmosis membranes and marking a breakthrough in membrane technology. The developed catalytic nanofiltration membrane amplifies the rate of peroxymonosulfate activation reactions by enriching its concentration near the membrane surface by a factor of 6.9 through concentration polarization. Confinement of the catalyst within the nanometre-scale pores greatly enhances the reactivity of the catalyst. Furthermore, the small pore size (<1.2 nm) effectively rejects natural organic matter (NOM) and the salts formed during the catalytic processes, thereby minimizing the interference of NOM within the active layer and preventing secondary contamination from salts, minimizing their interference in oxidative contaminant transformation. The optimized catalytic nanofiltration membrane demonstrated exceptional contaminant removal efficiency, maintaining close to 100% efficiency over 500 hours of continuous cross-flow filtration, and its fabrication was scaled up to the industrial scale through a roll-to-roll process, highlighting its practical viability for real-world applications. A catalytic nanofiltration membrane achieves the simultaneous removal of salts and small, neutral organic pollutants via oxidant enrichment at the membrane surface and confinement of the catalyst within nanometre-scale pores.