Preparation of superhydrophilic-underwater superoleophobic silica nanorods modified fiber membrane for efficient oil-in-water emulsion separation

Silica nanorods modified fiber membranes were successfully fabricated for the separation of emulsions by filtration deposition method. Compared to the unmodified membranes, the arithmetic mean and root mean square of the membranes were 5.69 μm and 9.71 μm, with an improvement of 39.8% and 46.0%, respectively. Roughness increases improved hydrophilicity and underwater oleophobicity of the membrane. The instantaneous water contact angle (WCA) and underwater oil contact angle (UOCA) reached 0° and 151.92°, showing excellent superhydrophilic and underwater superoleophobic properties. The structural stability of the membranes was demonstrated by testing the mass and microstructural changes after continuous ultrasonic treatment, where the mass loss was only 5.42% and no significant changes in the microstructure were observed. Moreover, following immersion treatment with acid, alkali, and saline solutions, the maximum loss of membrane mass was only 1.20% and it remained underwater oleophobic, displaying excellent chemical stability. The separation efficiency of the silica nanorods modified fiber membrane for oil-in-water emulsions was as high as 96%, and the separation flux was above 1900 L m−2 h−1·bar−1. The separation efficiency of the membranes was consistently maintained above 96% for 5 cycles.