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

• Published in: Journal of membrane science 2022-03, Vol.645, p.120204, Article 120204
• Main Authors: Yang, Yang, Lai, Qiaoyun, Mahmud, Sakil, Lu, Jiangyan, Zhang, Gaosheng, Huang, Zehui, Wu, Qihang, Zeng, Qingyi, Huang, Yongshi, Lei, Huifang, Xiong, Zhu
• Format: Article
• Language: English
• Subjects: Composite membranes; Emulsion separation; Photocatalysis cleaning; Rutile nano-titanium dioxide; Superhydrophilicity
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2021.120204

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/m2•h to ∼43 L/m2•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. •OH, •O2− and 1O2) 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. [Display omitted] •TiO2 coating is constructed on the polymeric membrane surfaces via bio-inspired sol-gel method.•The membrane exhibits excellent super-wetting, water penetration, and underwater oil repellency.•The membrane can separate the tricky crude oil emulsion with high-efficiency and good robustness.•TiO2 coating enables the membrane with photoactive self-cleaning in the absence of chemicals.