Superhydrophilicity and underwater superoleophobicity TiO ₂ /Al ₂ O ₃ composite membrane with ultra low oil adhesion for highly efficient oil-in-water emulsions separation

To improve the separation efficiency and decrease fouling of the membranes used in oil-in-water emulsions separation, a superhydrophilic and underwater superoleophobic TiO ₂ /Al ₂ O ₃ composite membrane with ultra low oil adhesion was designed. TiO ₂ nanorod arrays were prepared on Al ₂ O ₃ porous ceramic membrane surface by simple magnetron sputtering and hydrothermal oxidation. The microstructure and surface photosensitivity of TiO ₂ nanorod array-coated ceramic membrane can effectively increase the efficiency of oil-water separation and reduce the degree of surface fouling. The layer of TiO ₂ nanorod arrays not only reduced the pore size of traditional ceramic membrane (enhanced sieving effect of porous structures) but also endowed its superhydrophilicity (enhanced flux) and underwater superoleophobicity (enhanced oil/water selectivity and antifouling). Based on the superhydrophilicity (water contact angle (WCA) of 0°) and underwater superoleophobicity (oil contact angle (OCA) higher than 150°) of ceramic membrane, oil droplets were blocked by the membrane (oil-water separation efficiency 99.1% under gravity) and water will pass (flux is maintained at 41.8 L/(m ² h) under gravity). It also has excellent anti-fouling ability due to the ultra-low oil adhesion force (0.084 mN) of the TiO ₂ nanorod array-coating after UV irradiation. These features, combined with energy-saving, low-cost and easy-to-scale manufacturing schemes will be of great versatility and practicality in environmental rehabilitation and wastewater purification.