Superhydrophilic and Oil-Resistant SiO₂/PU Fiber Membrane for Oil-In-Water Emulsion Separation under Gravity

A polyurethane membrane with interlayer channels was developed through electrospinning to separate oily sewage. To enhance its hydrophilicity, hydrophilic silica particles were grafted onto the fiber surface, creating a rough surface. This was done by treating the membrane with oxygen plasma to generate active sites, which were then coupled with 3-aminopropyltriethoxysilane, followed by adding the membrane to a hydrolytic solution of tetraethyl orthosilicate. The resultant membrane had a low water contact angle of 23.3 degrees and excellent underwater oleophobicity, with a high-underwater oil contact angle (varied from 155.9 to 159.7 degrees) and underwater oil sliding angle (ranged from 4.0 to 4.6 degrees) for different types of oils. In addition, the prepared membrane had a good moisture-evaporation rate (4.2 g/h) and water-absorption capacity (273%). It is also oil-resistant and self-cleaning in water, and could efficiently separating oil-in-water emulsion under gravity, with an initial separation flux of 2864 L/m(2)/h. During cyclic separation of emulsion, the membrane had the oil-retention rate of more than 99.0%, and the final separation flux of the membrane was maintained at 25 L/m(2)/h.