Separation membranes with underliquid dual superlyophobicity have recently caused widespread concern due to their switchable separation of oil–water mixtures and emulsions. However, the fabrication of the reported underliquid dual superlyophobic membranes is difficult, and the design of the underliquid dual superlyophobic surface of these membranes is challenging because of their complex surface composition. Theoretically, underliquid dual superlyophobicity is an underliquid Cassie state attainable by the synergy of the underliquid dual lyophobic surface and the construction of a high-roughness surface. Herein, we fabricated an underliquid dual superlyophobic membrane by combining underliquid dual lyophobic polyvinylidene fluoride (PVDF) and TiO2 nanowires. PVDF-modified TiO2 nanowire membranes with underliquid dual superlyophobicity were prepared via a simple adsorption and filtration approach. PVDF was coated onto TiO2 nanowires to form a PVDF layer with a thickness of 6 nm. The PVDF modification provided flexibility to the fragile TiO2 nanowires membrane and changed its wettability from underwater superoleophobicity/underoil superhydrophilicity to underliquid dual superlyophobicity. The PVDF-modified TiO2 nanowires membrane efficiently separated both oil-in-water and water-in-oil emulsions. The binary cooperative effect between the TiO2 nanowires and the coated PVDF layer was responsible for the underliquid dual superlyophobicity.
Yutang Kang,Shihui Jiao,Yue Zhao,Zhenwei Zhang,Boran Wang,Guangsheng Pang
A stainless steel mesh supported TiO 2 nanowires membrane is prepared by heating hydrogen titanate nanowires deposited on stainless steel mesh. The stainless steel mesh supported TiO 2 nanowires membrane exhibits superhydrophilic and underwater superoleophobic property. The water contact angles in air of the stainless steel mesh supported TiO 2 nanowires membrane is 0° and the underwater oil contact angles (gasoline, n-hexadecane, hexamethylene and methylbenzene) are >150°. Both of surfactant-free oil-in-water mixtures and surfactant-stabilized emulsions are separated with a high permeation flux of >10 6 L m − 2 h − 1 bar − 1 and a separation efficiency of >99.1%. The stainless steel mesh supported TiO 2 nanowires membrane exhibits good resistant to fouling, and the possible organic pollutants are easy to be removed by heat treatment and the superhydrophilic and underwater superoleophobic property is recovered.
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