Preparation Of Superhydrophilic-underwater Super-oleophobic Membrane Material And Its Research On Oil-water Separation

Water Crisis in our daily life remains to be a crucial problem that we humankind are confronted with.The pollutants in water are usually including insoluble oil contaminates and soluble contaminates like dyes.As for the treatment of oily wastewater,the traditional methods could not meet the growing demand for more efficient and lower energy consuming technologies.In recent years,the newly emerged materials with special wetting properties have drown great attention,these materials are thought to be very promising for the application on oil/water separation.Usually,these special wetting materials can be divided into two classes,which including the superhydrophobic-superoleophilic materials and superhydrophilic-underwater superoleophobic materials.Since this paper is mainly focus on the treatment of oil-in-water emulsions,the superhydrophilic-underwater superoleophobic materials are better than the superhydrophobic-superoleophilic materials because the underwater oleophilicity is beneficial for the antifouling performance.Herein,this paper is mainly focus on finding the simply fabrication of different kinds of underwater superoleophobic membranes and study their performance on oily waste water treatment.In the first part,this paper is focus on the modification of the traditional polymer based membrane-polyvinylidene fluoride(PVDF)membrane.Based on the law of obtain superwetting which including proper roughness and proper hydrophilic/hydrophobic modification,the hydrophilic TiO2 nanoparticles are anchored on the PVDF membrane surface with the assistance of dopamine and a silane coupling agent(KH550).The modified membrane obtained best performance when the ratio between dopamine and KH550 was 1:1 and the amount of TiO2 was 40mg.The main role of TiO2 nanoparticles is to form rough structure on the membrane surface,and the dopamine with KH550 are act as linking agent and hydrophilicity modifier.All the as-prepared membranes were characterized by SEM,ATR-FTIR,XPS and so on.The wettability and oil/water separation of these membranes were also evaluated.Results have shown that the flux of this kind of membrane varies from 400?600 L·m-2·h-1 and it's separation efficiency for different oil in water emulsion are all around 99%.In the second part,this paper is focus on the simultaneously separation of both insoluble oil and soluble dyes in water.And the newly emerged graphene oxide membrane was choosing since it has shown great many advantages than the traditional polymer membranes.The halloysite nanotubes(HNTs)was composited with GO and assembled as a composite membrane through vacuum-filtration.When the ratio between GO and PHNTs is 1:1,and after addition of ethidene diamine,the as-prepared membrane has shown best performance.The HNTs can not only enlarge the interlamellar spacing and thus enhancing water flux,but also forming rough structure on the membrane surface which can help reaching special wettability.Besides that,the HNTs was pre-modified with dopamine to enhancing its dispersity,and the ethidene diamine was introduced to modify hydrophilicity and offering more active sites for dye absorbing.All the as-prepared membranes were characterized by SEM,XPS and so on.The wettability,dye separation,oil/water separation and simultaneously separation of both insoluble oil and soluble dyes in water performance of these membranes were also evaluated,results have shown that the rejection ratio for both dyes and oils in wastewater of this membrane have both achieved 99%.