Simple graft modification of reverse osmosis membrane to improve the permeability and antifouling performance

Membrane fouling remains a critical bottleneck, limiting the long-term operational stability of reverse osmosis (RO) membranes and causing decreased water permeability, elevated energy consumption, and reduced membrane durability. In this study, a fouling-resistant RO membrane was fabricated by grafting 1,3-diaminoguanidine monohydrochloride (DAGH) monomer onto a nascent polyamide (PA) layer via secondary interfacial polymerization (SIP). ATR-FTIR and XPS analyses confirmed the successful grafting of DAGH. The modified membrane exhibited enhanced hydrophilicity and a significantly reduced surface negative charge. Water permeability increased by 36.1 % (from 3.6 to 4.9 L m −2 h −1 bar −1 ), while salt rejection slightly decreased from 99.2 % to 98.7 %. With increasing grafting concentration, the water contact angle decreased from 78° to 62°, indicating enhanced hydrophilicity, while the surface negative charge was significantly reduced. Compared to the pristine membrane, the sample membranes demonstrated superior antifouling performance in dynamic fouling tests; specifically, the flux recovery rates (FRR) against bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB) were 23.2 % and 9.4 % higher than those of the pristine membrane, respectively. Notably, even for the negatively charged surfactant sodium lauryl sulfate (SDS), the modified membrane maintained comparable flux recovery to the original membrane. This facile and efficient DAGH grafting strategy not only achieves high permeability and excellent antifouling properties but also provides a promising approach for designing fouling-resistant RO membranes in desalination applications. • Small guanidine molecules were anchored onto RO membranes via the SIP method. • Water contact angle decreased from 78 ° to 62 ° , significantly enhancing hydrophilicity. • The RO membranes achieved higher water flux while retaining high NaCl rejection. • Flux recovery rates against BSA and CTAB improved by 23.2 % and 9.4 %, respectively.