Slippery Amphiphilic Antifouling Loose Nanofiltration Membrane with “Double-Defense” Functionalities for High-Salinity Organic Wastewater Sustainable Management

Abstract

Loose nanofiltration (LNF) holds potential for sustainable management of high-salinity organic wastewater through precise organics/salts fractionation, but practical application is constrained by severe organic–inorganic combined fouling. Herein, we propose a “double-defense” antifouling strategy and develop a slippery amphiphilic LNF membrane via facile stepwise surface modification. A hydrophilic branched polyethylenimine (PEI) network was first cross-linked onto a polyamide (PA) substrate to form a fouling-resistant protection layer, followed by covalent grafting of liquid-like polydimethylsiloxane (PDMS) brushes to confer a slippery, fouling-release surface. The PEI layer acts as a hydration and electrostatic barrier to repel organic-cation complexes and scale precursors, while the slippery PDMS layer with high mobility and low surface energy minimizes interfacial interactions and strengthens hydraulic shear responsiveness. During the concentration of authentic leachate membrane bioreactor (MBR) effluent, the optimized membrane showed superior antifouling performance: low flux decline ratio (FDR) of 41.6% and high flux recovery ratio (FRR) of 98.1%, outperforming a commercial PA membrane (FDR 91.2%, FRR 78.4%). It also delivered an organics/salts fractionation selectivity 7.8 times that of the commercial membrane, demonstrating multiple cycles stability. This rationally designed architecture offers a practical solution for challenging wastewater and is extensible to other PA-based membrane systems in environmental applications.