Smart pH-Responsive nanofibrous membranes with reversible wettability for efficient oil/water and emulsion separation

In response to the increasingly complex composition of industrial oily wastewater, the design of multifunctional separation materials capable of achieving phase-selective separation and efficient demulsification has become a major research focus. This study employed electrospinning to fabricate a novel nanofibrous membrane. The membrane was prepared from a blend containing the rationally designed, pH-responsive triblock copolymer poly(4-vinylpyridine)- block -poly(2-hydroxyethyl methacrylate)- block -poly( tert -butyl methacrylate) (P4VP- b -PHEMA- b -P t BMA) and polyacrylonitrile (PAN). The resulting membrane exhibits a unique bidirectional separation capability, allowing for the controlled separation of either light or heavy oil-water mixtures by simply adjusting the pH of the aqueous environment. It achieves a maximum oil-phase flux of up to 12,800 L/(m 2 ·h) with 98.8% separation efficiency, while maintaining a stable water-phase flux around 8500 L/(m 2 ·h) and efficiencies above 99%. Furthermore, the membrane was capable of effectively disrupting and separating stable water-in-oil and oil-in-water emulsions. Across repeated tests with diverse oil-water systems, the membrane consistently demonstrated high flux, high separation efficiency, and excellent cycling stability, highlighting its great potential in the design of intelligent separation materials and the treatment of complex wastewater.