Upcycling of waste brick powder and PET as robust and flexible Janus membrane with asymmetric wettability for switchable emulsion separation

Superwetting membranes were widely studied in the field of oil/water separation due to their excellent separation efficiency and good recoverability, but they still suffer from the disadvantages of expensive reagents, complicated processes, and narrow scope of application. Herein, a robust and flexible Janus membrane with asymmetric wetting properties was constructed using discarded PET and bricks powder as building blocks, for various types of emulsions separation. Given the cross-linking effect of acrylic resin, the superhydrophilic crushed waste bricks powder (WBP) was orderly assembled on the electrospinning PET nanofiber membrane, achieving asymmetric wettability on each side: the high-hydrophobic PET side had underwater superoleophilicity, while superhydrophilic WBP side had underwater superoleophobicity. Janus membrane exhibit excellent corrosion resistance and can maintain stable contact angles in different pH environments. Due to its highly porous and surface anisotropic nature, Janus membrane showed excellent separation efficiency and separation flux for both oil-in-water emulsions (separation efficiency up to 99.4%, separation flux up to 196 L m−2 h−1) and oil-in-water emulsions (separation efficiency up to 99.3%, separation flux up to 792 L m−2 h−1 bar−1). More importantly, Janus membranes exhibited outstanding reusability. This Janus membrane shows great potential in the fields of waste upcycling and emulsion separation.