Beadlike Porous Fibrous Membrane with Switchable Wettability for Efficient Oil/Water Separation

The development of switchable wettability membranes with high permeation fluxes is crucial for oily sewage treatment. A hierarchical beadlike porous PS fibrous membrane with pH-switchable wettability was precisely fabricated by nonsolvent-induced phase separation during electrospinning, followed by UV photografting copolymers of 2-(dimethylamino) ethyl acrylate (DMAEA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate (TFOA). The designed unique structure notably increases the roughness of surface and enhances superwettability. Protonation of the amine groups on the fibers triggered by an acid solution (pH < 2) induces underwater super-oleophobicity, which in turn causes superoleophilicity in a neutral or basic solution. The as-prepared fibrous membrane can effectively separate the hexane/water mixture with an oil flux of 10 186.8 L m(-2) h(-1) and a separation efficiency of 99.2% only driven by gravity. Especially, excellent separation performances (water fluxes) were also realized for other oil/water mixtures with higher viscosity by switching the wettability from superoleophilicity to hydrophilicity. Moreover, the as-prepared fibrous membrane can also be applied to a continuous T-shaped tube device delivering a high handling capacity of 6631.5 L m(-2) h(-1), which provides the oily sewage treatment with a facile strategy in practical application.