| In recent years,industrialized production,human life and oil extraction have brought about the discharge of large amounts of oily wastewater,which seriously threatens to the ecological environment and human health.The superwetting twodimensional membrane materials show great potential in the field of oil-water separation due to their high selectivity for both oil and water phases.However,there are some issues of poor corrosion resistance to acid,alkali,and salt as well as low separation efficiency in the practical application for separation membrane materials.Besides,the actual wastewater often contains organic dyes in addition to insoluble oil,and the removal of these organic dyes is also an urgent problem that needs to be addressed immediately.Currently,the nanofibrous oil-water separation membranes with photodegradation ability for organic dyes have attracted a lot of attention.But most of the reports only focus on the degradation of water-soluble organic dyes,the degradation of oil-soluble organic dyes is then rarely reported.The reason is that the photocatalysts on separation membranes should possess hydrophobicity/oleophilicity in order to separate and photodegrade oil-water mixtures or emulsions containing oily dyes.However,many metal oxide photocatalysts are inherently hydrophilic,and the hydrophobic modification is required.Although surface modification of photocatalysts with fluorinated organic compounds can bring hydrophobicity,the organic coating on the surface is easily photodegraded by light,quickly giving rise to the hydrophilic surface again.To solve the above problems,a kind of superhydrophobic/superoleophilic nanofibrous membrane was reported,which possesses stable superhydrophobicity against acid/alkali/salt and light.Moreover,the separation performance of the membrane for oil-water mixtures as well as water-in-oil emulsions and photodegradation performance for oily dyes were investigated.The main contents are as follows:(1)Firstly,the superhydrophobic/superoleophilic polyvinylidene fluoride/polytetrafluoroethylene(PVDF/PTFE)nanofibrous membrane was prepared by electrospinning technology.The additional ammonia in electrospun solution could generate a dehydrofluorination reaction between PVDF and PTFE chains,inducing cross-linking among the polymer chains and increasing the loading of PTFE on the surface of PVDF nanofibers.The effects of PTFE content on the morphology,pore structure and wettability of the membranes were investigated.Due to the strong bond between PVDF fibers and PTFE particles,the PVDF/PTFE membrane shows excellent structural stability and superhydrophobicity under various harsh environments(immersion in acid/alkali/salt solution,xenon lamp irradiation,contact with hot water),leading to high-efficiency separation for oil-water mixtures and water-in-oil emulsions.(2)In order to further improve the oil-water separation performance of PVDF/PTFE membrane and endow it with photodegradation ability for organic dyes,the superhydrophobic/superoleophilic PVDF/PTFE@titanium dioxide(TiO2)nanofibrous membranes were developed through the combination of dehydrofluorination and one-pot hydrothermal fluorination process on basis of the PVDF/PTFE nanofibrous membranes.The fluorosilane was added into hydrothermal reaction solution,and involved into the interior of TiO2 to form crosslinking network across the formation of TiO2.The as-prepared PVDF/PTFE@TiO2 membrane exhibits superhydrophobicity under various harsh environments(immersion in acid/alkali/salt solution,xenon lamp irradiation,contact with hot water).Furthermore,the separation efficiency of PVDF/PTFE@TiO2 membrane for water-in-oil emulsion is superior to that of PVDF/PTFE membrane.Additionally,the PVDF/PTFE@TiO2 membranes possess durable photodegradation for organic dyes in water-in-oil emulsion.More importantly,the photodegradation efficiency of the PVDF/PTFE@TiO2 membranes for oil-soluble dyes remains above 95%even after 10 cycles. |
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