Asymmetric Janus nanofibrous membrane with microspheres/nano-nets for switchable oil-water emulsions separation

Oil-water separation membranes with excellent performance are crucial for addressing the issue of marine oil pollution and treating industrial wastewater. To overcome the limitations of traditional polymeric membranes, such as large pore sizes and limited emulsion selectivity, an asymmetric Janus nanofibrous membrane with switchable separation capabilities for oil–water emulsions was developed through a synergistic combination of layer-by-layer electrospinning and electrospraying techniques. The Janus membrane consists of a hydrophilic layer with a fine pore structure (0.46 μ m) and a hydrophobic layer composed of nano-nets connected by nanofibers (56 nm) and microspheres. The distinctive structural configuration endows the membrane with dual functionality: the hydrophilic surface demonstrates superhydrophilicity (0°) and underwater oleophobicity (140°), facilitating efficient oil-in-water emulsions separation with a flux of 4233 L m -2 h −1 and a separation efficiency of 99.36 % at 5 kPa. Conversely, the hydrophobic surface exhibits superoleophilicity (0°) and underwater superhydrophobicity (>150°), achieving permeation flux of 1887 L m -2 h −1 with 99.32 % separation efficiency for water-in-oil emulsions under gravity. Furthermore, the membrane demonstrates unidirectional moisture transport capability, superior mechanical strength, and recyclability.