Research On Preparation And Application In Oil-Water Separation Of Janus Membrane

Oil-water separation technology has wide requirements in life and industial.In recent years,using a selective wetting membrane to separate oil-water mixtures has attracted people’s attention.Selective wetting membranes mainly include hydrophobic-oleophilic membrane,hydrophilic-submerged oleophobic membrane and hydrophilic-oleophobic membrane.The selective wetting membrane has high efficiency and low energy consumption when separating oil-water mixtures.Howerer,the mesh holes of membrane are easily contaminated by impurities,the working life of the mesh film is short,and the rough structure on the surface has poor mechanical strength.Bilateral asymmetric superwetting membrane(Janus membrane)is a new type of superwetting membrane,which consists of porous material and has different wettability on its two srufaces.Janus membrane showed unidirectional liquid transport along the thickness.Because the unidirectional transport property can increase the separating speed in oil-water mixtures,especially in emulsions,it has a promising application prospect.In this dissertation,the mechanism,preparation methods and applications of Janus membrane were studied.The two-sided differential wettability model of Janus membrane was based on its own structure and wettability,and the two-sided differential wettability of Janus membrane was discussed.Moreover,we analyzed the pressure-bearing capacity curves of different types of Janus membranes and the influence laws of variables,including contact angle,pore size ratio and hydrophobic layer thickness.The mechanism of agglomeration and permeation of Janus membranes for oil-water separation was discussed.Finally,we proposed preparation methods of Janus membrane for oil-water separation.Based on the surface free energy theory and the wettability state,the membrane substrates were prepared by combining low surface energy substances with micro-/nano rough structures.Then Janus membranes of wettability gradient and wettability mutation types were prepared by exporing UV light and spraying methods,respectively.In order to determine the basic properties of Janus membranes,the membranes were characterized in four aspects,including wettability,unidirectional transport properties,surface micromorphology and surface chemical elements.The critical breakthrough pressures on both sides of the prepared Janus membranes were measured to validate the theoretical model of Janus membranes.By using the prepared Janus membranes,we achieved the separation of oil in water and water in oil emulsions,verified the mechanism of agglomeration and permeation during oil-water separation,and the ability of Janus membranes to promote emulsion seperation.In the end,we realized the application of Janus membranes in the collection and transportation of liquids.In this dissertation,we investigated the theoretical model and preparation methods of Janus membranes,which are less studied at present.The special wettability model of Janus membranes helps to analyze the asymmetric properties of various Janus membranes in multiphase applications.A mechanism of Janus membrane in oil-water separation is proposed and verified,which helps to analyze the phenomenon that Janus membrane can promote oil-water separation.This dissertation is valuable not only in theory,but also in practice.The theory can promote the design and practical application of Janus membranes in the fields of energy harvesting,oil-water separation and oil pollution treatment.