Hierarchically Structured Porous Polyamide-Imide Membrane for Switchable Emulsion Separation

The development of advanced membranes with switchable superwettability has attracted considerable attention for the efficient treatment of oily wastewater. However, challenges persist in designing and fabricating such membranes through straightforward methods. In this study, a novel strategy is presented to design switchable superwettable membranes based on micro/nano-structured porous surfaces and surface chemical composition reorganization. A commercial amphiphilic polymer, polyamide-imide (Torlon), is fabricated into a porous symmetric membrane with a hierarchical surface structure using a one-step non-solvent-induced phase separation method. By leveraging the surface reorganization capability of amphiphilic polymers and the hierarchically porous structure, the resulting membranes demonstrate exceptional superamphiphilicity in air, underwater superoleophobicity, and underoil superhydrophobicity. These properties enable ultrahigh permeance and separation efficiency for oil-in-water, water-in-oil, and crude oil/water emulsions through a gravity-driven process, eliminating the need for external energy. Furthermore, the membranes exhibit excellent antifouling and self-cleaning performance, maintaining stable operation over multiple cycles. This work provides an innovative and scalable approach to next-generation switchable superwettable membranes with broad potential applications in oily wastewater treatment and beyond.