Study On Visible Light Catalysis Of Graphite Carbon Nitride Based Material And Its Surface Modification On Cement Products

With the development of social economy and industrial level,the problem of environmental pollution is becoming more and more serious.In view of the environmental problems that arise,photocatalytic technology is an effective method of pollution control.Graphite carbon nitride?g-C₃N₄?is a new type of catalyst with stable performance,visible light catalytic degradation,high decomposition efficiency for pollutants and relatively low cost.It forms a heterogeneous material with semiconductors that match the band gap to improve its visible light catalytic performance.Graphite carbon nitride is used on the surface of bulk cement-based materials to achieve effective degradation of pollutants on the surface of cement-based materials.This can contribute to environmental governance.This article focuses on the preparation of graphite phase carbon nitride and its heterostructure materials and methods of improving photocatalytic performance.And it is used to treat the cement surface to obtain the effect of visible light degradation of organic pollutants on the cement surface to achieve the purpose of self-cleaning.Firstly,g-C₃N₄ was successfully prepared by heat shrinking method.The optimal preparation method is optimized by adjusting the type of precursor and the preparation temperature.Through research and analysis,it is concluded that urea is the best preparation precursor,and 550?is the best preparation temperature.The g-C₃N₄ prepared under this condition has poor crystallinity and the microscopic morphology is a random stack of nano-sized sheets with pores in the middle.These structural features can provide more active sites for g-C₃N₄,so that the photocatalytic activity of the catalyst is improved.At the same time,g-C₃N₄ prepared with urea as the precursor at 550?has good photocatalytic stability.Secondly,the graphite carbon nitride-titanium dioxide heterogeneous material was successfully synthesized by in-situ growth method and ultrasonic composite method.Changeing in the ratio of graphite carbon nitride to titanium dioxide will have an impact on the structure and performance of heterogeneous materials.When the ratio of graphite carbon nitride to titanium dioxide was 4,the photocatalytic performance was the most superior compared with graphite carbon nitride.At the same time,the same ratio of graphite carbonitride-titanium dioxide heterogeneous materials was prepared by ultrasonic compound method.It was consistent with the crystal structure,micro-morphology,band gap and visible light catalytic performance of heterogeneous materials obtained by in-situ growth method.Thirdly,graphite carbon nitride-silica heterogeneous material was successfully prepared with thermal condensation by using silica and urea as raw materials.The factors that affect the performance of graphite carbon nitride-silica heterogeneous materials were explored by adjusting the specific surface area and incorporation of silica.The addition of nano-silica will introduce defects in the energy band of g-C₃N₄,which changed the band gap.Under the same mixing ratio,the modification effect of silica with a specific surface area of 300 m²/g was better than that of silica with a specific surface area of 200 m²/g and 380 m²/g.When the specific surface area of silica was 300 m²/g and the amount of silica was 0.15 g,the performance of the obtained catalyst was the best.Under this condition,the microstructure is a uniform mosaic structure,the specific surface area becomes larger,the pores become larger,and the average pore diameter becomes smaller.These factors can provide more active sites to improve the visible light catalytic performance of the catalyst.Fourthly,by using graphite carbon nitride-silicon dioxide heterogeneous material as the coating raw material,the surface treatment of cement was carried out by one-side immersion and painting.It can degrade dyes under visible light irradiation.By comparing the uniformity and photocatalytic activity of the coating,it was concluded that the brushing was more used for the surface treatment of cement than the one-sided immersion.The bonding mechanism was studied by using the mixed reaction of calcium hydroxide and graphite carbon nitride-silicon dioxide heterogeneous materials.The combination of graphite carbon nitride-silica heterogeneous material and cement was combined by the pozzolanic reaction between silica and calcium hydroxide in cement to form C-S-H gel.