Ionic Liquid-Mediated Structural Regulation of Reverse Osmosis Membranes for Enhanced Antifouling Performance against Diverse Organic Foulants

Reverse osmosis (RO) membranes face significant performance degradation when treating complex wastewater, with membrane fouling induced by surfactants being particularly prominent. In this study, an ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), was introduced to regulate the interfacial polymerization between hydrazine (Hz) and trimesoyl chloride (TMC). This approach successfully fabricated an Hz-based polyamide RO membrane with superior structural characteristics and a significant antifouling performance. Compared to conventional polyamide membranes prepared with m-phenylenediamine, the Hz monomer, featuring a linear molecular structure and higher reactivity, generated a smoother and more hydrophilic membrane surface. Meanwhile, the IL effectively retarded the diffusion of Hz through hydrogen bonding and electrostatic interactions, achieving a more controllable polymerization process and, thereby, the formation of an ultrathin selective layer with low surface roughness and narrow pore size distribution. The resulting membrane exhibited significantly enhanced water permeability while maintaining an excellent salt rejection. Due to both favorable surface properties and uniform microstructure, the membrane exhibited universal resistance to various types of organic foulants, such as surfactants with opposite charges, demonstrated by minimal flux decline during fouling and high permeability recovery after simple cleaning. This membrane design strategy and the revealed antifouling mechanisms provide new avenues for developing high-performance RO membranes adequate for complex wastewater systems.