Enhanced performance of polyamide membrane through hydrophilic and porous substrate fabricated by surface segregation method

Polyamide (PA) reverse osmosis thin-film composite (RO TFC) membranes constructed via interfacial polymerization (IP) process have been extensively employed in seawater desalination, and the crosslinking degree and thickness of PA layer play crucial role on their practical performance. Herein, an in-situ surface segregation strategy was adopted to fabricate hydrophilic and porous substrate with dopamine (DA) as surface segregation agent, thereby effectively regulating the IP process for enhanced desalination. During substrate fabrication process, DA self-polymerized to generate polydopamine (PDA), subsequently PDA segregated into surface, which could enrich amine monomers in the aqueous phase and slow their diffusion toward the organic phase, through hydrogen bonding and π-π interactions between PDA and amine monomers. Accordingly, the crosslinking degree increased from 79.1 % to 89.9 %, particularly improving boric acid rejection from 71.3 % to 88.9 %. Meanwhile, the thickness of PA layer decreased to 48.0 nm. The optimized membrane exhibited a water permeability of 1.91 L m −2  h −1 bar −1 and NaCl rejection of 99.9 %, while maintaining excellent stability over 100 h of continuous operation. Furthermore, the membrane showed outstanding desalination performance for real seawater, demonstrating that fabricating substrate through surface segregation method offered an efficient and easy pathway for high-performance RO membranes.