Superhydrophilic and underwater superoleophobic Ti foam with robust nanoarray structures of TiO2 for effective oil-in-water emulsion separation

In this work, a superhydrophilic and underwater superoleophobic Ti foam with TiO2 nanoarrays was facilely fabricated via the hydrothermal treatment and proton exchange method. Taking advantages of the constructed hierarchical structures and the high surface energy of TiO2, the Ti foam exhibits excellent superwetting behaviors to water and ultralow oil adhesion property with the underwater oil contact angle (OCA) of 166 degrees and the sliding angle (OSA) lower than 3 degrees. Meanwhile, the as-prepared foam can be applied for separating various oil-inwater emulsions with 99% separation efficiency and high permeation fluxes. Additionally, it performed good anti-fouling and self-cleaning property, which had stable separation performance even for 50 cycles of repeated use. Importantly, the hierarchical structured sample showed outstanding chemical stability and robust mechanical durability under various chemical corrosions, physical abrasion and vibration without obvious reduction of the separation efficiency. It is expected that superhydrophilic Ti foam with nanoarray structures constructed by this facile method would be a practical candidate in oily wastewater purification, due to its excellent wetting property, good self-cleaning capacity, robust mechanical durability, as well as superior chemical stability.