Oil-water receiving membrane with sub-10 nm surfactant layer for long-lasting oil-water separation

Oil fouling is an inherent threaten of membrane-based separation of oil-water emulsion, while common physical sieving membrane separation and coalescence demulsification fail to achieve long term applications and combat severe water flux declines. We hereby report an “oil-water-receiving” membrane with anomalous wettability constructed by sub-10 nm Tween 80 assembly on hydrophobic PVDF nanofibers to establish independent water and oil transmembrane passageway. Water can go through the membrane freely along the hydrophilic nanofiber surface. While emulsified oils were diverted beneath the ultra-thin hydrophilic layer and captured by PVDF bulk to form coalesced oil phase and discharged out of the nanofibrous membrane as continuous macroscopic oil phase. The membrane showed stable permeate flux as high as 536 ± 40 L m−2 h−1 bar−1 after 10 h of continuously filtering oil-in-water emulsions. The conformation assembly of surfactants with hydrophilic and hydrophobic chains provides a new strategy to fabricate anti-fouling membranes for oil/water separation.