Study On Wettability Regulation Of Stainless Steel Meshes And Their Application In Oil-water Separation

In recent years,with the rapid development of the global economy,the surrounding environment has been filled with a large amount of industrial waste water and domestic sewage,as well as oil spills in the oil extraction and transportation in the ocean,which have caused major harm to human health and the ecological environment.How to quickly and effectively treat these oily water has become an urgent need for social development.Based on its high oil-water separation efficiency,oil-water separation materials with special wettability surfaces have attracted widespread attention.However,the existing special wettability materials have certain defects in their properties and preparation processes,such as high material costs,complex preparation processes,poor performance,and so on.Aiming at these problems,this paper proposes a material with controllable wettability that is economical,simple in process and excellent in performance.According to the characteristics of wettability materials,the oil-water separation experiment is designed,and the performance of oil-water separation is emphasized.Firstly,this article uses common stainless steel mesh as the base and focuses on the two key wettability factors of surface microstructure and surface chemical composition to prepare controllable wettability materials.Zn O coatings are grown on the surface of 304 stainless steel mesh by hydrothermal method.Because Zn O has natural oxygen vacancies,and water molecules are easily distributed into the oxygen vacancies to form hydrophilic groups,the surfaces demonstrate a super-hydrophilic state,and it takes 0.48 s for the water droplets to spread completely on the surface.In order to realize the reversible transition from super-hydrophilic to super-hydrophobic,a layer of fatty acid monomolecular was self-assembled on the surface of the Zn O coating,and a stainless steel mesh with a controllable wettability surface was successfully prepared.The results show that the surface is covered with a micro-nano binary rough structure coating composed of Zn O nanorods;after being modified by fatty acids with different chain lengths,the surface wettability changes from superhydrophilic to super-hydrophobic,and the contact angle ranges from 0° to 158°.While for oils,the surface always maintains a lyophilic state.The separation efficiency is as high as 98%,and the separation efficiency for different oil-water mixtures still reached more than 85% after 50 repeated separation tests.The combination of fatty acid is easily to combine stainless steel mesh surface,thus a chemical etching method was selected to construct a binary micro-nano rough structure on the stainless steel mesh,and then the rough structure was modified by the self-assembled molecular film technology to make the fatty acid and the stainless steel have a excellent combination.The results show that the surface of the stainless steel mesh presents a three-dimensional rough morphology consisting of peaks and valleys of different sizes;the surface self-assembled molecular film exhibits different wetting properties due to different chain lengths.With the increase of the carbon chain length,the surface realizes the transition from hydrophilic to superhydrophobic,the contact angle ranges from 45 to 153°.The separation efficiency was as high as 96%.After 50 repeated oil-water separation tests,the separation efficiency decreased slightly.Taking into account the actual application environment,the corrosion resistance test was also done,and the results show that the treated mesh is more resistant to corrosion than the original one,and the corrosion rate is greatly reduced.In order to be more practical applications,a high-efficiency oil-water separation mesh was prepared using a two-step method with super-hydrophobic and superlipophilic characteristics.In the experiment,simple chemical etching and vapor deposition methods were selected to prepare super-hydrophobic and super-lipophilic stainless steel mesh.The contact angle of the surface after FAS modification for water droplets can reach 151°.The oil with lower surface energy spreads quickly on the surface of the mesh.After the oil-water separation test,the filter has a high separation efficiency of 90% for different oil-water mixtures.Also,the corrosion resistance of the meshs is significantly improved,and its reuse performance is also developed.