Solar-driven pH-responsive oil–water separation membranes for effective oil–water emulsion separation

Oil spills and industrial wastewater discharge have inflicted severe damage upon the ecological environment and human health. Therefore, the development of an environmentally friendly and pollution-free membrane material for oil–water separation is imperative. This study presents the development of a novel oil–water separation material (PP–PPy–pHR) that is environmentally benign and capable of switching between wetting properties. The material was synthesised by dopamine modification, treatment with a pH-responsive polymer and the use of a high-efficiency photothermal layer composed of self-assembled polypyrrole (PPy), and it not only separates incompatible oil–water mixtures but also efficiently separates oil–water emulsions under different pH conditions. Due to the good photothermal effect of PPy, the evaporation rate of PP–PPy–pHR composite membrane loaded with PPy was 3.95 times higher than that of pure water for oily wastewater. In addition, the PPy–pHR composite membrane exhibited excellent durability and high stability in extremely acidic and alkaline solutions, showing remarkable potential for oil–water separation applications.