Laser Biomimetic Manufacturing Of Janus Stainless Steel Film And Its Application In Wastewater Treatment

The ancients said that the lotus leaves the mud without being dyed,and the clean lotus is washed without being evil.This statement actually reveals the special wettability of the lotus leaf surface.Due to the superhydrophobic characteristics of the lotus leaf upper surface,the dirt on the surface can be effectively removed by liquid drop rolling.In fact,it is not only the lotus leaves that have this special wettability in nature.After billions of years of evolution,all living things in nature have evolved various "equipment" to resist the adverse environment around them.The special wettability of animal and plant epidermis comes from the micro-nano structure and special chemical composition of their epidermis,making their epidermis better able to remove pollutants,collect water or isolate water.Bionic manufacturing technology is to process devices with similar functions by imitating the characteristics of various organisms in nature and apply them to production and manufacturing.In this paper,Janus materials with opposite wettability on both sides are processed by nanosecond laser biomimetic manufacturing technology,and the influence of different microstructures on the wettability of stainless steel film is explored by processing different micro-textures on the surface.Janus stainless steel membrane was applied in microporous aeration,and the effect of Janus stainless steel membrane on the rate of ammonia nitrogen decomposition by nitrifying bacteria was analyzed.The main contents of this article include:(1)Examples of different biological applications of wettability in nature are listed,and the relevant principles of wettability,the development process of Janus materials and the neighborhood where they have been put into use are discussed.This paper introduces the relevant background of sewage treatment,and the introducti on of the main content and purpose of this paper.(2)The nanosecond laser processing system is described and the interaction mec hanism between the two when the laser beam is exposed to the material surface.The c hanges of stainless steel surface roughness and droplet contact angle after changing th e laser working parameters are studied.The results show that the surface wettability of stainless steel film with well shaped microtextures has the greatest influence among several microtextures.The wettability of stainless steel film material processed will also change by reducing the spacing of microtextures.After the material processed by nanosecond laser is modified by fluorosilane reagent with low surface energy,the stainless steel surface that originally presents high surface energy property will be transformed into low surface energy property,so the ultra-hydrophilic surface processed by nanosecond laser will be transformed into ultra-hydrophobic surface due to the effect of surface fluorosilane reagent.(3)Through the ablation of nanosecond laser,the micro-nano structure is machined on the surface of both sides of the stainless steel film,and then the micro-nano drilling is carried out on the film.Finally,the surface of one side is modified with low surface energy reagent through fluorosilane reagent,and the Janus stainless steel film with micropore array with opposite wettability on both sides is prepared.The super hydrophilic surface is the upper surface,and the super hydrophobic surface is the lower surface.The upper surface can make the gas quickly separate from the material surface due to its hydrophobic characteristics,and the lower surface can effectively prevent the liquid from penetrating into the aeration chamber through the micropores due to its hydrophobic characteristics.The experiment shows that by controlling the pore size and pore spacing of the micropores,the size of the bubbles at the time of release can be adjusted,and then the ratio of the residence time of the gas in the water to that dissolved in the water can be controlled.(4)The experimental sewage is treated by biofilm method,and the biological characteristics of aerobic autotrophic bacteria nitrifying bacteria are used to decompose the ammonia nitrogen in the sewage.By comparing the change of ammonia nitrogen content in experimental sewage without aeration,using ordinary commercial aerator,using double-sided hydrophobic stainless steel membrane aeration and using Janus stainless steel membrane aeration,the effect of using Janus stainless steel membrane aerator on the decomposition rate of ammonia nitrogen organics by nitrifying bacteria was explored.The research results of this paper are helpful to improve the working efficiency of ammonia nitrogen in sewage treatment,and a simple,efficient,stable and low-cost method for preparing Janus material is proposed...