Flexible, durable and magnetic nanofibrous membrane with pH-switchable wettability for efficient on-demand oil/water separation

One of the most pervasive environmental issues is water contaminated with various oils. Developing an efficient and novel functional membrane for oil/water separation is urgently needed. Herein, a flexible, durable and magnetic pH-responsive F3O4/MA–TiO2/PI electrospun nanofibrous membrane (ENM) was fabricated via an electrospinning and green dip-coating route. Combining the rough hierarchical structure and pH-responsive wettability, the as-prepared hybrid membrane can controllably separate a range of not only heavy oil/water but also light oil/water mixtures by only adjusting the pH of the aqueous medium. Both separations exhibit a large flux and outstanding efficiency for the tested oil/water mixtures even after 20 reuse cycles due to the hierarchical structure and flexibility of the membrane. In addition, the flexibility and magnetism of the membrane make it easily removed with a magnet after the separation of the oil/water mixtures. More importantly, the as-prepared membrane not only has excellent stability towards high temperature, corrosive organic solvent/salt solution immersion, and UV irradiation but also shows great resistance to mechanical abrasion and ultrasonic treatment, and the preparation method is facile, environmentally friendly, and cost-effective. Thus, such a membrane may offer exciting opportunities in the application of oily wastewater treatment and on-demand oil/water separation.