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Potocatalytic antifouling membrane with dense nano-TiO2 coating for efficient oil-in-water emulsion separation and self-cleaning

Journal: J. Membr. Sci., Volume 645, MAR 5

Authors: Yang, Yang; Lai, Qiaoyun; Mahmud, Sakil; Lu, Jiangyan; Zhang, Gaosheng; Huang, Zehui; Wu, Qihang; Zeng, Qingyi; Huang, Yongshi; Lei, Huifang; Xiong, Zhu

Organizations: National Natural Science Foundation of China [42077159, 52170083, 51808143]; Excellent Youth Fund Project of Natural Science Foundation of Hunan Province [2021JJ20007]; Innovative Training Program for College students [XJ202011078407, XJ202011078048, XJ202111078171]

Keywords: Composite membranes; Rutile nano-titanium dioxide; Superhydrophilicity; Emulsion separation; Photocatalysis cleaning

Herein, a dense rutile nano-titanium dioxide (TiO2) coating was constructed on the nonwoven fabric (NWF) membrane surfaces via the bio-inspired TiO2 sol-gel method. The mineralization of nano-TiO2 was large-scale and uniform on the non-woven fabrics (NWF) surface, reducing membrane surface roughness and pore sizes; nevertheless, largely improving the dynamic water super-wetting, water penetration, and underwater oil repellency due to the excellent water affinity. Nuclear magnetic resonance (NMR) revealed the hydration layer of the NWF was reinforced by the surface-mineralized nano-TiO2, thus preventing the bovine serum albumin (BSA) and emulsified oil droplets from fouling. Even after the 180 min of continuous emulsion separation, the mineralized NWF (TiO2-PDA/PEI-NWF-M) only suffered from the mild decline of permeation fluxes from-55 L/ m(2).h to-43 L/m(2).h and oil rejection from-94% to-83%, respectively. After illuminated under UV light, it was recovered successfully because of the in-situ generation of reactive species (e.g. center dot OH, center dot O-2(-) and O-1(2)) on TiO2 weakened the interaction of foulants on the membrane surface. The photoactive self-cleaning provided the TiO2- PDA/PEI-NWF-M with better efficiency of oil-fouling reduction, permeation fluxes recovery, and oil removal than those of simple water and harsh NaClO washing. Most importantly, the TiO2-PDA/PEI-NWF-M maintained its surface physical and chemical characteristics after vigorous cross-flow shearing for 48 h. It provided the practical potential in developing the high-efficient and free-chemical self-cleaning with the high and stable flux recovery for the tricky crude oil/water emulsion remediation.