Bioinspired superwetting fibrous skin with hierarchical roughness for efficient oily water separation

Developing superwetting membranes with interconnected pore and multi-scale roughness for efficient oily water separation is significant but challenging owing to the limitations of low water flux and membrane fouling. Herein, we report a scalable method to develop superwetting membranes with superhydrophilicity and underwater superoleophobicity for oily water separation. This novel approach, composed of electrospinning/electrospraying of polyacrylonitrile (PAN), was to fabricate rough sphere membrane substrate, followed by in-situ polymerization of dopamine/polyethyleneimine (DA/PEI) to positively charge the fiber skin and then subsequent immersed into the negatively charged Ludox solution to construct rough membrane surface via electrostatic attraction. Benefiting from the rough sphere surface of the fibrous skin layer, the resultant membrane displayed micro/nanostructured surfaces with intriguing in-air superhydrophilicity of 0° and underwater superoleophobicity of 166° as well as robust oil-proof pressure of 83.55 kPa. As a proof-of-concept, the resultant membrane achieved high water flux and oil rejection efficiency as well as fantastic durability and antifouling performance toward the separation of highly emulsified oily water. The integration of electrospinning/electrospraying with bioinspired method is also expected to fabricate superwetting sphere surface membrane with interconnected pores for other selective separation applications.