Substrate-independent fabrication of superhydrophilic membrane based on dopamine methacrylamide and zwitterionic substance for effective oil-in-water emulsion separation

• The membrane for oil-water emulsion separation was fabricated by DMA deposition following MPC grafting. • The modification method developed was substrate-independent. • The modified membrane exhibited three times water flux of the pristine membranes. • The modified membranes demonstrated higher oil-in-water emulsion fluxes, enhanced oil rejection, and better anti-fouling performances. The fouling caused by oils and other contaminants is the critical obstacle for the membrane application in oil-in-water emulsion separation. To increase the hydrophilicity of the membrane, a substrate-independent approach was developed, in which the catechol derivative dopamine methacrylamide (DMA) was deposited on the membrane followed by UV copolymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC). Both hydrophobic membrane, poly(vinylidene fluoride), and hydrophilic membrane, polyethersulfone, became superhydrophilic after modification. The obtained membranes were characterized by Fourier-transform infrared spectroscopy (FTIR), Drop shape analyzer (DSA), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and membrane pore-size analyzer. Additionally, pure water flux and oil-in-water emulsion separation performance were evaluated for the selected samples. The pure water flux of the modified membrane was increased from 490 L/m 2 h and 612 L/m 2 h to 1564 L/m 2 h and 2219 L/m 2 h under the optimal concentration of MPC for PVDF and PES membranes, respectively, which is more than three times that of the pristine membrane. Furthermore, the obtained membrane demonstrated enhanced oil-in-water emulsion separation efficiency as well as superior antifouling capabilities. The developed strategy is not restricted by the membrane materials, and might provide a new strategy for membrane surface modification aimed at oil-in-water emulsion separation.