Structurally integrated janus polylactic acid fibrous membranes for oil-water separation

Oily wastewater presents a considerable risk to human health as well as the ecological environment, making the advancement of an effective oil/water separation membrane an urgent global priority. Herein, an asymmetric wettable Janus nanofiber membrane made of polylactic acid (PLA) nanofiber membrane was created through a sequential multilayer electrospinning strategy using two different precursors: PLA/cellulose diacetate (PLA/ CDA) and PLA/carbon nanotubes (PLA/CNTs). The PLA/CNTs nanofiber membrane exhibited hydrophobicity, with water contact angles above 133 degrees in air, while the PLA/CDA nanofiber membrane exhibited favorable hydrophilicity. The membranes, which exhibit completely opposite wettabilities on either side of the Janus structure, demonstrated excellent separation efficiency of 97.5 %, 97.04 %, and 95.31 % and high flux of up to 21,073.57 L m- 2 h- 1, 1792.81 L m- 2 h- 1, and 974.36 L m- 2 h- 1 for water-carbon tetrachloride mixtures (state of incompatibility), petroleum ether-in-water emulsions and water-in-petroleum ether emulsions respectively. Most notably, the Janus PLA nanofibrous membranes with a unique micro-nanostructure maintained a desirable separation efficiency of over 89 % for water-in-oil emulsions and more than 87 % for oil-in-water emulsions following 10 cycles without any form of treatment. Therefore, this Janus PLA nanofiber membrane with asymmetric wettability, which is developed using the layer-by-layer electrospinning strategy, has enormous potential for sustainable and effective oil/water separation applications.