A Rapid and Facile Preparation of PVDF–PG/KH550 Bioinspired Membrane for Efficient Separation of Oil-in-Water Emulsions

In recent years, modified membranes for oil–water separation have garnered significant attention. However, the complexity of the process, low efficiency, and serious oil contamination have been the main obstacles to its application. Hence, there is an urgent need to explore simple, environmentally friendly modification methods. Inspired by adhesive bioproteins and diatomaceous silica, this study presents a simple, low-cost, and environmentally friendly biomimetic coating strategy to prepare a highly efficient oil–water separation membrane with convenient separation and excellent resistance to oil fouling. Using pyrogallic acid (PG) and silane coupling agent KH550, a one-step modification of the poly(vinylidene fluoride) (PVDF) microfiltration membrane (MF) was conducted, transitioning the surface wettability of the PVDF membrane from highly hydrophobic to superhydrophilic. This resulted in layered nanoscale papillary structures on the PVDF–MF surface, imparting superhydrophilicity and underwater superoleophobicity, along with excellent oil–water separation capability. Under a transmembrane pressure of 0.85 bar, systematic testing of the modified membrane demonstrated that the stable flux of the emulsion is approximately 950 L m–2 h–1, with an oil rejection rate exceeding 99% and significantly improved fouling resistance, as well as excellent chemical stability and salt resistance. The "green" in situ biomimetic silicification strategy is equally applicable to inert materials such as polytetrafluoroethylene (PTFE) membranes, demonstrating its significant potential for application on other materials.