Electro-driven pore expansion of pH-responsive membranes to enhance antifouling performance for efficient oil-water separation

Superhydrophilic oil-water separation membranes exhibit fixed interfacial properties, which limits their ability to withstand oil fouling. Enhancing the in-situ anti-fouling performance of membranes dynamically at the interface is challenging. Here, a structurally adjustable pH-responsive membrane for oil-water separation was prepared, combined with patterned silver gel to impart conductivity. Acting as a cathode, this membrane electrolyzes water to generate OH − ions that directly regulate the interfacial pH. The generated OH − ions trigger the responsive layers' contraction, which results in the expansion of the membrane's pore size. Such structural adjustments could shorten the oil-water-solid three-phase contact line of pinned oil droplets to reduce the adhension force, creating interfacial disturbances that enhance the anti-fouling capabilities of membrane. By this way, lubricants and crude oils adhered to the membrane could be de-wetted in 32 s without other assistance. Meanwhile, the expansion of the membrane's pore size increases the washing efficiency. The flux recovery rate after 300 min long-term cycling can reach up to 97.6 % without additional reagents. The fabricated anti-fouling membrane significantly improves separation efficiency and holds great potential for applications in oily wastewater treatment.