Fabrication Of Novel Superhydrophilic Composite Coatings On Polyvinylidene Fluoride Membrane And Application In Oil-Water Separation

In order to solve the problem of oily sewage treatment,scientists and engineers have put forward many countermeasures.As a common separation material in membrane separation technology,polyvinylidene fluoride membrane has good mechanical and chemical stability and tiny pore structure,which is an excellent choice for separating oil-water emulsion.However,due to the high hydrophobicity and the affinity for oil,polyvinylidene fluoride membrane is easy to be polluted and blocked by oil,which seriously affects the efficiency and flux of oil-water separation.In this study,the hydrophilic modification of polyvinylidene fluoride membrane was carried out,and the superhydrophilic/underwater superoleophobic separation membrane material was developed,which was successfully applied to the separation of oil-water emulsion.On this basis,the wettability was further optimized and improved,and the anti-oil coating in air was constructed,and the superhydrophilic/oleophobic separation membrane material which could be directly used without pre-wetting was prepared.The specific contents and results of this study are as follows:（1）The superhydrophilic coating was successfully prepared by simple impregnation method at room temperature by using proanthocyanidins andε-polylysine to construct unique hierarchical micro-nano rough structure on the surface of polyvinylidene fluoride membrane.The modified polyvinylivene fluoride membrane has superhydrophilic/underwater superoleophobic properties,water droplets can quickly infiltrate the membrane surface within 1.27 s,the maximum underwater oil contact angle of the film surface can reach 165±1.2°,and has excellent anti-fouling performance and self-cleaning ability for actual crude oil.The modified membrane can efficiently separate a variety of oil-in-water emulsions,with the highest separation efficiency and flux of 487.26L·m^-2h^-1 and 99.72%.In addition,when the membrane was exposed to air and immersed in water for 6 weeks,and immersed in different pH values and seawater for 24 hours,the underwater oil contact angle remained above 154°,while the water contact angle was always 0°,demonstrating excellent durability to different extreme environments.After testing,the superhydrophilic coating has good universality and can be applied to a variety of substrates,which has great application potential in the field of oil-water separation.（2）On the basis of superhydrophilic/underwater superoleophobic polyvinylidene fluoride membrane,FS-50 and inorganic nano SiO₂ particles were used to further optimize its infiltration performance and anti-fouling ability,and the protective coating with anti-oil performance under dry conditions was constructed.The superhydrophilic/oleophobic polyvinylidene fluoride membrane separation material was successfully developed.The modified separation membrane material can be used without pre-wetting.It can not only resist oil pollution under water,but also show good resistance to oil substances when dry.The oil contact angle in the air is up to 144±1.5°,the contact angle of water in the air is always 0°,and has excellent low adhesion performance.In addition,we observed and analyzed its surface morphology and chemical composition by a variety of characterization methods,tested and studied its various durability properties and oil-water separation properties,and elucidated the mechanism of superhydrophilic/oleophobic.The development of the coating can provide some reference for improving the antifouling performance of membrane materials.