Fabrication Of Water-based Superamphiphobic Composite Coatings And Their Application In Catalytic Filter

With the continuous strengthening of social environmental awareness,the air pollution caused by exhaust emissions from heavy industries such as cement and steelmaking has attracted widespread attention.Bag-type dust collectors and low-temperature selective catalytic reduction（SCR）catalysts are the core components of dust and nitrogen oxide（NOx）exhaust gas treatment in industrial exhaust gas.They are currently the most commercially used flue gas dust removal and denitration technologies.However,when the bag type dust collector works,the water vapor in the tail gas adheres to the surface of the filter bag,which easily causes the phenomenon of "sticky bags",which causes the filtration resistance of the filter bag to increase and the filtration efficiency to decrease.When water vapor contacts the catalyst,it will inactivate its toxicity,seriously affect the denitration efficiency of the catalyst,and reduce the service life.The effective treatment of dust,nitrogen oxides and other pollutants in industrial exhaust has been an important research direction in this field.Therefore,the research on preparation,moisture-proof,dust-proof properties and durability of superhydrophobic filter which can simultaneously removal of dust and NOx had been carried out.A water-based nano-superhydrophobic coating was prepared by a wet chemical method.The coating used water as a solvent,SiO₂ as rough units and FAS as a low surface energy substance.The orthogonal experiment method was used to study the reasonable ratio of the coating preparation.The coating process was also studied.The water-based superhydrophobic coating has a water static contact angles of 165.0±2.1°,a rolling angle of 1.0°,and has no change in wettability after 30 days at room temperature.It has good thermal stability which can still maintain superhydrophobicity after heat treatment at 300°C for 48 h.The PPS filter was treated by dip coating to prepare a superhydrophobic PPS filter.Compared with the PPS filter treated with a water-repellent agent on the market,the superhydrophobic PPS filter has excellent moisture resistance and breathability maintaining.In order to improve the adhesion of the superhydrophobic coating on the filter material,a waterbased superamphiphobic composite coating with a bottom surface and a water-based resin compound was prepared.The effect of the content of main components on the adhesion,hardness and abrasion resistance of the coating had been studyed.The reasonable ratio of the components obtained by the controlled variable method is: solvent: modified SiO₂ particles: WAC: F600 = 5: 2.5: 1: 1.The prepared coating has water and oil static contact angles of more than 160° and rolling angles of less than 10°.The coating can still maintain superamphiphobic property after 700 abrasion cycles by finger,80 abrasion meters by sandpaper,1000 abrasion cycles by abrasion resistance tester and 1000 abrasion milliliters by continuous water droplets.The coating is suitable for different substrates and has good thermal and chemical stability.Finally,a superhydrophobic catalyst was prepared based on the aforementioned wet chemical method.The effect of fluorine content on the wettability and denitration activity of the catalyst was studied.The reasonable ratio of FAS to the catalyst was 1:3,which results in good superhydrophobicity of the catalyst.Compared with the untreated catalyst,the coating has about 10%increase in denitration activity.Based on the above one-step method,a superhydrophobic biomimetic catalytic filter was prepared,and the static contact angle of the catalytic filter in water was 165.1±2.5°.Compared with the untreated composite filter material,the water and sulfur resistance of the superhydrophobic filter material has increased by 60% at 180°C,and it has good water and sulfur resistance.When the dust test is performed for 30 hours,the weight is reduced by 30%,which has better dustproof performance.The moisture-proof effect is increased by 90%,the breathability is slightly reduced,and it has good moisture-proofness.After being soaked in a strong acid-base solution at p H= 1 and p H = 13 for 96 hours,indicating good water repellency and good acid and alkali resistance.