Research On The Preparation And Performance Of A Special Wetting Film Based On Hydrotalcite-coated Stainless Steel Mesh

Inspired by nature,the preparation and application of bionic special wetting membranes,especially underwater superoleophobic and superamphiphobic coatings,having attracted widespread attention in the academic and industrial circles.superhydrophilic and underwater superoleophobic/superamphiphobic coatings have a wide range of applications in oil-water separation,self-cleaning,anti-corrosion,anti-fouling,and drag reduction.Traditional separation techniques often involve double sparse coating,high energy consumption,time consuming,high cost,and secondary pollution generally limiting membrane practical applications.Therefore,it is of practical significance to prepare environmentally-friendly,available and stable superhydrophilic underwater superleophobic/ultra-double-oleophobic coatings.This paper uses hydrothermal method to prepare hydrotalcite（LDH）coatings on stainless steel nets,and conducts research from the following three aspects:In this thesis,a layered bimetal hydroxide（LDH-SSM）stainless steel mesh（LDH-SSM）was prepared by hydrothermal synthesis using a layered bimetal hydroxide（LDH）as a membrane modification material and a stainless steel mesh as a substrate.The effects of different pore size conditions,LDH deposition modification and surface chemical modification on the structure and performance of the membrane were researched,and it was applied to oil-water separation and the application of membrane self-cleaning ability.This work is carried out mainly from the following three aspects:First of all,the original stainless steel mesh lacks a certain degree of roughness,however,consdering its excellent mechanical properties and corrosion resistance,LDH were introduced on the surface of stainless steel mesh（500 mesh）with a relatively large pore size by in-situ growth.And the LDH-SSM has outstandings super hydrophilicity and superoleophobicity in water for the LDH micro-nano coating.The wettability of different oil droplets and the separation performance of different kinds of oil-water mixtures were studied,as well as their chemical and mechanical stability.Reseach shows:LDH-SSM（500 mesh）,when separating oil-water mixture,the flux can reach up to⁴4.5 L m-2 s-1,and the separation efficiency is up to 99.2%.The underwater contact angles of different types of oil are above 150°,and the rolling angle an be as low as 2.5°,and it has good recycle performance.After the cycle,the flux and oil-water separation efficiency have not decreased significantly.At the same time,it still maintains superior performance in harsh solutions and has certain anti-wear properties.It is of significance to deal with oil leakage and oil recovery quickly.Secondly,in order to solve the problem that the modified stainless steel mesh membrane is generally difficult to separate the oil-water emulsion,based on the research in the previous chapter,this chapter uses a relatively small pore size 2300mesh stainless steel to first prepare LDH-SSM（2300）.Then,LDH@LDH-SSM was prepared based on it.The separation performance of the membrane for different kinds of oil-water emulsions and the stable performance of the membrane were studied.The uperhydrophilic underwater superoleophobic LDH@LDH-SSM still can maintain excellent self-cleaning ability to oil in water.Meanwhlie,it has relatively high flux and retention to separate diferent oil-water emulsion.The water flux of the emulsion can be as high as 4076 L m^-2 h^-1bar^-1 and the retention can be as high as 97.8%.For membrane formation in aqueous solution,the surface of LDH@LDH-SSM membrane prepared in hydrothermal of boric acid solution is denser and has better mechanical stability,and both sides of the membrane can realize the filtration of oil-water emulsion.Also,LDH@LDH-SSM has good regeneration performance and anti-pollution ability.After the oil-water emulsion is separated,the flux can be restored to a normal level by simple water cleaning.At the same time,the membrane can withstand the corrosion of a certain corrosion solution,and the flux still maintain above 3974L m^-2 h^-1bar^-1,and the retention is still above 97%.Finally,in order to achieve complete self-cleaning to water and oil in the air,based on the first work,a superhydrophobic and superoleophobic F-LDH-SSM（500mesh）membrane was fabricated.The wetting ability of different types of aqueous solutions and oils was studied,and the performance of hydrophobic and oleophobic oils under different concentrations,such as fluorination,fluorination temperature,and fluorination time was investigated.A series of F-LDH-SSM self-cleaning and stability test was carried out.The research found that the contact angle of F-LDH-SSM（500 mesh）to water is as high as 166.3°,and the rolling angle is about4.8.The contact angle for common oils is all 150°,and the rolling angle is less than10°.Under the high concentration of fluorosilane fluorination,the surface fluoride layer adversely affects the surface morphology of the F-LDH-SSM and affects the performance of the membrane.Lower temperature and higher temperature are not conducive to the fluorination.When the temperature rises to 80°C,the membrane even shows a lipophilic state.And the 60°C is a relatively good fluorination temperature;the fluorination time reaches to 18 h and above the time,the water or oil contact angle of F-LDH-SSM is hardly to change;in harsh solutions and extreme hot and cold environments,F-LDH-SSM still maintains excellent chemical stability,and the membrane also has a relatively good mechanical behavior.F-LDH-SSM,which has excellent self-cleaning ability and shows good anti-fouling performance,has certain significance for practical applications.