Multi-scale structure regulation of reverse osmosis membranes for high performance achieved by the co-solvent diethylene glycol dimethyl ether

The intrinsic structure of the polyamide separation layer fundamentally governs the performance of reverse osmosis (RO) membranes. In this study, environmentally friendly diethylene glycol dimethyl ether (DEGDME) was used as co -solvent to modulate the interfacial polymerization process and subsequently regulate the structure of the separation layers. Small-angle X-ray scattering (SAXS), alongwith conventional methods, was utilized to investigate the multi-scale structure of the separation layers, including morphology and aggregation at the nanometer scale. The fractal dimension ( P 2 ) derived from SAXS exhibited a strong linear relationship with the water permeability coefficient A ( R 2  = 0.9984), and an exponential relationship with NaCl permeability coefficient B ( R 2  = 0.9265) when the DEGDME content was not exceed 0.5 wt%. At a DEGDME content of 0.3 wt%, the water flux of the RO membrane reached 69.8 L·m −2 ·h −1 , exhibiting a 105.3 % increase compared to the original membrane, with no significant loss in NaCl rejection. Additionally, the RO membrane M-0.3 demonstrated excellent antifouling properties and long-term operational stability. Given the simplicity and efficacy of the co-solvent regulation method, it holds significant potential for practical applications.