In situ metal-polyphenol interfacial assembly tailored superwetting PES/SPES/MPN membranes for oil-in-water emulsion separation

Superhydrophilic and underwater superoleophobic membranes have recently attracted increased attention in oily wastewater treatment because of their potential to promote membrane permeability and minimize membrane fouling. Despite recent advances, the manipulation of membrane superwettability is usually achieved by coating functional layers on commercial hydrophobic porous substrates. The direct fabrication of super hydrophilic and underwater superoleophobic microporous membranes still remains a challenge. In this work, we provide a new in situ metal-polyphenol interfacial assembly strategy and prepare a new type of superwetting PES/SPES/MPN membranes. In the phase inversion of membrane formation, the coordination assembly of tannic acid (TA) and transition metal ions takes place alone with the solvent/nonsolvent exchange, resulting in the in situ deposition of metal-polyphenol networks (MPNs) on as-prepared polyether sulfone (PES)/sulfonated poly ether sulfone (SPES) membranes. The PES/SPES/MPN membranes exhibit hierarchical surfaces and bicontinuous pores, and the in situ deposited MPNs provide hydrophilic bases. Among them, the PES/SPES/TAFe(3+) membrane showed the highest superhydrophilicity and underwater superoleophobicity. Thanks to the excellent superhydrophilicity, the water flux of PES/SPES/TA-Fe3+ membrane can reach 4423 Lm(-2)h(-1). Moreover, the PES/SPES/TA-Fe3+ membrane exhibits high-performance for oil-in-water emulsion separation with high flux (>1500 Lm(-2)h(-1)), excellent oil rejection (>99.5%) and reliable enhanced antifouling and recycling performance. This study provides a novel and facile strategy for the direct fabrication of superwetting microporous membranes, and predicts the potential application of PES/SPES/MPN membranes in oily wastewater treatment.