Engineering Highly Permeable and Antifouling Polyamide RO Membranes via Interfacial Polymerization with Molecularly Designed Zwitterionic Surfactants

To address the urgent requirement for antifouling reverse osmosis (RO) membranes, this work presents an innovative interfacial polymerization (IP) strategy utilizing molecularly engineered zwitterionic surfactants. Three zwitterionic surfactants with identical hydrophilic heads but distinct hydrophobic tails were synthesized, each serves a dual function: regulating IP kinetics while incorporating into the polyamide (PA) network to confer inherent antifouling properties. The surfactant combining an aromatic ring and a long alkyl chain proved most effective, enhancing integration via π-π interactions and maximizing interfacial activity to yield a polyamide layer with superior density, hydrophilicity, and permeability. The resulting membrane achieves a balance of high water permeance (2.7 LMH/bar), outstanding salt rejection (99.6%), and excellent antifouling performance. In practical tests using real coking wastewater, it consistently outperformed a leading commercial antifouling membrane (DuPont FilmTec CR100) across multiple fouling-cleaning cycles. This study establishes a new paradigm in which tailored surfactant molecular design directly governs RO membrane properties and integrated performance, offering a promising pathway to next-generation RO membranes for challenging water treatment applications.