Thermo-responsive Membranes with Switchable Superhydrophilicity and Superhydrophobicity for Oil–Water Separation

Oil–water separation remains key in the development of technology for a range of applications. In this chapter, thermally responsive membranes with switchable superwettabilities used for controllable oil–water separation will be discussed. Superwetting membranes have been shown to be energy-efficient and cost-effective for the separation of oil–water mixtures or oil–water emulsions because the separation mechanism is based on the different interfacial effects of oil or water on the superwetting surface. These membranes show not only excellent separation efficiency, but also ultrahigh permeation flux. In recent years, on–off switchable separation of oil–water mixtures, separation of different kinds of oil-in-water emulsions and water-in-oil emulsions with the same membrane, and tuneable permeation flux have been achieved by introduction of a thermally responsive ability into the superwetting membranes. The challenges in this area are also outlined for further development of thermo-responsive membranes with superwetting surfaces for controllable oil–water separation and practical applications.