Dynamic Hydrogen-Bonded Hydration Networks Mitigate Organic–Inorganic Fouling in Nanofiltration

Abstract

Hydration layers are widely recognized as the molecular basis of antifouling membrane interfaces, yet their role is still largely viewed through a static barrier picture. The dynamic response of hydrated membrane–water interfaces to approaching foulants, particularly under organic–inorganic mixed fouling conditions, remains poorly understood. Here, using poly(sulfobetaine methacrylate) (pSBMA)-modified nanofiltration membranes as a model zwitterionic interface, we reveal that fouling reversibility is strongly influenced by the dynamic stability of hydrogen-bonded hydration networks at the membrane–water interface. Molecular simulations combined with sum-frequency generation spectroscopy demonstrate that pSBMA sustains a strongly hydrogen-bonded interfacial water structure with preferential water dipole orientation under silicate and alginate perturbation, thereby suppressing long-lived foulant residence near the membrane surface. Real-time surface plasmon resonance measurements further confirm weakened irreversible foulant anchoring and enhanced interfacial reversibility. As a result, pSBMA-modified nanofiltration membranes reduced flux decline during mixed-foulant filtration to ∼6% and achieved >91% flux recovery after physical cleaning, accompanied by lower organic and inorganic foulant residuals. Repeated filtration–cleaning tests with real secondary effluent further confirmed nearly complete flux recovery in complex water matrices. These findings revisit zwitterionic antifouling by shifting the focus from static surface hydration to the dynamic stability of hydrogen-bonded hydration networks, providing a mechanistic basis for understanding and regulating fouling reversibility.