Robust special wettability materials for oil-water separation: Mechanisms and strategies

Special wettability materials have been favored by researchers in recent years, and have played a great role in a variety of fields such as fog water collection, anti-fog, anti-icing, self-cleaning, etc. Especially in the field of oilwater separation, the frequent occurrence of offshore oil spills has seriously endangered the ecological environment. Inspired by nature, researchers have developed and manufactured a lot of bionic special wettability materials, which are expected to be effective in oil-water separation and solve the problem. However, the inherent fragility of these materials significantly limits their practical applications. There is an urgent need to fabricate special wettability materials with excellent mechanical and chemical stability through appropriate surface structure and composition design. In this review, the wettability theory and failure mechanisms of special wettability materials used for oil-water separation are reviewed, followed by a summary of test methods used to characterize durability. Methods to improve the durability of materials in recent years are described. Firstly, starting from the substrate material, the appropriate substrate material is selected according to the working environment. Secondly, micro/nano hierarchical structures can enhance the robustness and durability of materials. For coating-type materials, strengthening the bond between the substrate material and the coating is a common and effective strategy. Chemical bonds can be formed between them, and the binder can also be introduced. Moreover, endowing the material with self-healing properties is also an efficient approach. The final section summarizes the challenges in this field and offers an outlook, with the expectation of enabling large-scale, real-world applications.