Recent advances in electrospinning smart membranes for oil/water separation

Human activities produce large amounts of oily wastewater, which needs to be treated to protect the environment. Membrane separation methods have attracted attention because of their high efficiency, however, most of the current membrane separation methods can only be used for one of water-in-oil or oil-in-water emulsions, and may even be optimized for narrower composition ranges, limiting their applicability. To solve this problem, smart oil/water separation membranes have been proposed. Smart membranes refer to membranes whose wettability can be transformed under specific conditions, including Janus membranes, pre-wetting membranes and responsive membranes. This paper reviews smart oil/water separation membranes prepared using electrospinning methods. Stimuli responsive membranes change their physical properties upon changes in pH, exposure to light or heat, or upon application of an electrical or magnetic field. This review focuses specifically on changes in wettability, and not on changes in other properties. This article describes in detail the preparation of these membranes, the advantages and disadvantages of each membrane, the theoretical support and the wettability transition mechanisms used in the separation process. Illustrative examples of stimuli responsive materials for smart membranes are provided. Finally, the challenges and future opportunities for smart membranes in oil/water separation are summarized.