Dual-functional polyethyleneimine engineered interfacial polymerization for ultra-high flux reverse osmosis membranes with moderate salt rejection

Reverse osmosis (RO) membranes are widely recognized for their high solute rejection, yet their relatively low water flux leads to elevated energy consumption. Addressing the growing demand for water treatment across diverse salinity levels-from hypersaline brines to micro-polluted water sources-requires RO membranes with ultra-high flux (more than 100 L m-2 h-1) and moderate salt rejection (about 95 %), which remain scarce in current technologies. To bridge this gap, we developed a novel RO membrane by strategically regulating the interfacial polymerization process using polyethyleneimine (PEI). This approach reduces polyamide network cross-linking by limiting aqueous monomer diffusion, thereby slowing reaction kinetics and forming a thinner, more permeable selective layer. The optimized membrane achieved an exceptional water flux of 157.9 L m-2 h-1 while maintaining a NaCl rejection of 94.5 %. Structural characterization reveals enhanced hydrophilicity (water contact angle decreased from 68.8 degrees to 35.9 degrees), a thinner selective layer (450 nm vs. 220 nm), and reduced cross-linking degree (99.1 % vs 86.7 %.), collectively contributing to the significant flux improvement. Comparative evaluation with commercial membranes (SW30, BW30, XLE, NF90) demonstrate superior desalination efficiency, highlighting its potential for applications requiring high throughput and moderate selectivity, such as industrial wastewater reuse and drinking water treatment. This research presents a scalable strategy for tailoring the membrane separation performance, advancing energy-efficient desalination technologies.