Synthetic expanded polytetrafluoroethylene (ePTFE) membrane has a wide range of applications, including aerosol and dust removal, and exhibits high dust-removing efficiency, high air permeability, and cost-effectiveness. However, the intrinsic oleophilic surface of ePTFE limits its application in the oil-bearing gas–solid separation process. Herein, we report a surface modification method to prepare amphiphobic ePTFE membranes via coating of a layer of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFTMS) – modified nano-SiO2 onto the surface of ePTFE fibers. The oil contact angle of the modified ePTFE membranes was increased from 0 to 123°, while retaining the initial water contact angle of 142°. The amphiphobic membrane shows excellent oil aerosol filtration efficiency with a comparative low pressure drop and high oil rejection rate of 99.5%. Remarkably, the membrane can be reused after simple rinsing with water. The oil aerosol filtration efficiency of membrane remained as high as 98.5% after five cycles of filtration and cleaning.
Dongyan Li,Jian Hu,Ze-Xian Low,Zhaoxiang Zhong,Yong Wang
Expanded polytetrafluoroethylene (ePTFE) is one of the most common membrane materials, but the intrinsic hydrophobic nature is a major reason for deteriorating performances in water purification. In this work, the influences of atomic layer deposition (ALD) seeding and subsequent ZnO nanorod (NR) growth on the surface morphologies and water permeability of ePTFE membranes was investigated. ZnO-ALD ePTFE membrane showed an order of magnitude increase in water permeation, owing to the substantial increase in surface hydrophilicity and surface area. The best-performing ZnO NRs membrane had a pure water flux (PWF) of 1764.3 L·m–2·h–1 (compared to 153.8 L·m–2·h–1 of the pristine ePTFE membrane). Suspension filtration experiments indicate that the ZnO NRs filter showed an increase of steady-state flux of more than 5 times and an increase of 29.7% in retention compared to that of the ePTFE membrane. Significantly, the novel ZnO NR filter exhibited good photocatalytic performance as demonstrated in the degradation of methyl orange (MO) solution. Therefore, the functionalized membrane can potentially overcome the inherent limitation in the trade-off effect and imply their superiority for controlling water quality.
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