Study On Preparation And Properties Of Nanofiber/Silica Coated Composite Membrane For Oil-water Separation

The problem of water pollution cannot be ignored in the process of the rapid progress of human society.Among them,oil pollution,as a kind of water pollution,is increasingly attracting people’s attention due to its severe destruction.Efficient and convenient membrane treatment methods are increasingly being studied and applied to related oil and water treatment problems.However,most of the preparation methods for oil-water separation membranes today cannot be realized in large-scale production and applications because of high costs and complicated process steps.The search for a method for preparing an oil-water separation membrane that is easy to operate and has a low cost is crucial for the research in related fields and the real realization of large-scale production in the future.In this paper,the oil-water separation composite membrane was prepared by using hydrophilic oleophobic silica（SiO₂）nanoparticles as coating.The hydrophilicity of the PVA-co-PE nanofibers was added to improve the film-formation performance of the silica nanoparticles.The influence of the composition and preparation process of PVA-co-PE nanofibers/SiO2 suspension on the film-formation of the coating was studied.The coating was then applied to the surface of the substrate.The effects of PVA-co-PE nanofiber addition amount,coating method,substrate mesh number,and gram weight on the micromorphology,hydrophilicity,lipophilicity,underwater oleophobicity,and separation rate of the PVA-co-PE nanofibers/SiO₂ composite membrane was studied using SEM and contact angle measuring instrument.The oil-water mixtures were formulated with various organic reagents,oils,and deionized water,and they were dyed separately.The separation effect of composite membranes on oil-water mixtures was studied under gravity-driven conditions.The separation efficiency of gravity-driven composite membranes were measured by a formula which was relaed to the weight of the mixture.The results showed that when the PVA-co-PE nanofibers were added at 50%,the hydrophilicity of the composite membrane was the best,and the oil contact angle under water was about 140°.When the mesh number of the substrate is 150and the gram weight is 11GSM,the separation rate of the composite membrane is the largest.At this time,the composite membrane can effectively separate a variety of oil-water mixtures under the action of gravity,and the separation efficiency is over 94%.Using a nanofiber membrane as a substrate,the coating is applied to a substrate to obtain a composite membrane that can separate the oil-water emulsion under pressure drive.The microstructure,hydrophilicity and separation efficiency of PVA-co-PE nanofibers/SiO₂composite membranes under different pressures and repeated use times were studied by SEM,Fourier transform infrared spectrometer,contact angle measuring instrument,optical microscope and total organic carbon analyzer.The results show that the pressure range can be applied on the composite membrane in the range of 0.025-0.07 MPa;within this pressure range,the composite membrane can effectively separate the stable oil-water emulsion,and the separation efficiency is as high as 99%.In the pressure range of 0.025-0.07 MPa,the flux of the membrane gradually increases as the pressure increases,but decreases after repeated use for many times.