Surface Segregation-Induced Superwetting Separation Membranes with Hierarchical Surface Structures and Internalized Gel Networks

The porous polymeric membranes prepared by conventional nonsolvent-induced phase separation (NIPS) suffer from notorious fouling pollution during oil/water separation. Herein, an improved one-step NIPS strategy is proposed to fabricate anti-fouling polyethersulfone (PES) based membranes that bear hierarchically spherical structures on the interface and an internalized gel network. More specifically, the hydrogen bonding between hydrophilic additives of polyvinylpyrrolidone (PVP) and tannic acid (TA), as well as Fe3+-TA coordination interaction are orchestrated to modulate their surface segregation behaviors during NIPS, leading to in situ generation of the interfacial assembled nanospheres and embedded gel networks in the PES matrix. Thanks to the synergistic effect of these dual antifouling barriers, the optimized membrane exhibits super-hydrophilic/underwater super-oleophobic properties, and displays high efficiency as well as good recyclability in separating surfactant stabilized oil-in-water emulsions. In addition, this improved NIPS methodology allows dip coating of various porous substrates to separate diverse oil/water mixtures, which also exhibits good anti-fouling ability. Basically, this study will provide new insights for design of anti-pollution oil/water separation materials by the phase inversion method.