Study On Preparation And Photocatalytic Degradation Performance Of G-C₃N₄ New Asphalt Pavement Materials

With the continuous increase of the number of cars,the traffic environment and urban air pollution are becoming more and more serious.Automobile exhaust emission is harmful to human health and urban living environment.The development of semiconductor photocatalysis technology provides a new way to control air pollution.The nano TiO₂ that traditional semiconductor photocatalytic materials is widely used in the photocatalytic degradation of pollutants because of the advantages of mild reaction conditions,no two pollution etc,but its large band gap leads to low utilization of solar energy and can only be excited by ultraviolet light less than 380 nm.In recent years,the emerging non metallic semiconductor photocatalytic materials graphite phase carbon nitride?g-C₃N₄?can be used less than 460 nm blue violet light-emitting catalytic reaction,to broaden the scope of application of photocatalytic materials.In a muffle furnace,the g-C₃N₄ was respectively prepared by calcining melamine,two cyanide two amine,urea at the high temperature.The methylene blue degradation test was used to measure the photocatalytic effect and adsorption capacity of each product,and the ability to degrade polluted gases was evaluated by degrading NO gas under visible light.The products were characterized by XRD,FT-IR,TG-DSC and SEM.Based on the test results,select the melamine as a g-C₃N₄ precursor to prepare composite photocatalyst.The effects of calcination temperature and calcination time on the photocatalytic activity of g-C₃N₄ prepared by melamine were studied.The results showed that g-C₃N₄ was prepared by three kinds of precursors,and the characteristic peak of the triazine ring was found in the photocatalytic structure unit of three;The yield of the product that was prepared by melamine was 44.23%,and the photocatalytic efficiency was about 36.21%,therefore,it was preferable that melamine was the precursor of g-C₃N₄.With the increase of calcination temperature,the photocatalytic efficiency increased first and then decreased,and the maximum photocatalytic efficiency reached 38.25% at the temperature of 550;the effect of different calcination time on the visible light photocatalytic efficiency of g-C₃N₄ prepared by melamine was small.The g-C₃N₄/ TiO₂ composite photocatalyst was prepared by calcining mixture of melamine and nano TiO₂ in a muffle furnace at the high temperature.The dispersion was prepared by two methods: solid phase co mixing and aqueous dispersion.The experiments of single factor included calcination temperature,calcining time,compound proportion were carried out to evaluate the photocatalytic degradation.XRD,FT-IR,TG-DSC,XPS,EA,TEM,SEM were used to characterize the composite photocatalyst.The results show that the recombination of g-C₃N₄ and TiO₂ increases the photogenerated carrier transfer,reduces the recombination of photogenerated electron hole pairs,and improves the photocatalytic efficiency;under the condition of calcining 5h at 550 ?,the catalytic efficiency of melamine and TiO₂ by mass ratio of 2:1 was the highest,and the highest catalytic efficiency was more than 48%.The effect of the composite photocatalyst on the penetration,softening point and ductility of the three indexes of the matrix asphalt material was evaluated by means of the direct mixing of the 70# matrix asphalt and the spraying of Marshall.It was also evaluated that the photocatalytic degradation performance of visible light.The way of photocatalytic material loading asphalt material was analyzed.The results show that the direct addition of matrix asphalt has little influence on the penetration and softening point of asphalt,but the ductility decreases greatly;the photocatalytic effect of photocatalytic asphalt is poor and the catalytic reaction is hindered because the catalyst is completely wrapped by asphalt materials.The photocatalytic effect of dispersion liquid spraying Marshall specimen is better,but it needs to be improved in the application of asphalt pavement.It is necessary to choose the excellent adhesive material and the better connection method to load the photocatalyst on the asphalt material.Two kinds of methods that direct powder mixing and dispersion were used to prepare the photocatalytic emulsified asphalt material by blending the composite photocatalyst with cationic,anionic and nonionic emulsified asphalt.Fluorescence microscopy was used to observe the distribution of catalyst in emulsified asphalt.And its application effect was evaluated combined with the photocatalytic property.The results show that the kinds of emulsified asphalt has little influence on the catalyst,but the solid content has a great influence on the catalytic activity;the photocatalyst is distributed in the interstitial space and the surface of the asphalt,which is beneficial to the photocatalytic reaction.when the emulsified asphalt is broken,the defects and micropores formed by water evaporation on the asphalt surface are favorable for the photocatalytic reaction.The photodegradation rate can reach 20% by blending the dispersion and emulsified asphalt.