Smart Materials with Special Wettability toward Oil/Water Separation and Recovery

Clean water resources are fundamental to global health. Oil spills and industrial organic pollutants have caused severe water contamination, leading to severe shortages of clean water and threatening every species in the ecosystem. Therefore, it is of great urgency to deal with the oily wastewater worldwide. Recently, advanced materials with special wettability have been developed and employed for oily wastewater remediation. It is commonly known that the synergistic effect between surface chemical composition and surface morphology is the key factor to realize the opposite wettability of oil and water, which dominates the selective wetting or absorption of oils/water. On this basis, smart materials with switchable superwettability and various intelligent functions have been developed for selective oil/water separation through reasonable design of chemical composition and surface microstructure. In this chapter, the separation mechanisms of oil/water mixture and various fabrication methods of superwettable separation materials are summarized. The superwettable smart materials with intelligent functions, including photocatalytic, self-healing, and smart oil/water separation materials with switchable wettability, are emphatically introduced, which can realize self-cleaning, self-healing, and efficient and controllable oily wastewater treatment. Moreover, the fabrication technologies, representative studies, separation mechanisms, and separation efficiency of these different separation materials are briefly discussed. Lastly, the challenges and outlook for oil/water separation based on the special wettability materials are discussed. It is expected that smart separation materials can achieve industrial scale production and be put into use for oil spills and industrial oily wastewater treatment in the near future.