Preparation Of G-C₃N₄-based Photocatalyst And Its Visible Light Catalytic Performance

At present,rapid advances in technology and industry have brought high-quality living standards.A large number of pollutants enter the water environment,and it is difficult for traditional technology to completely degrade them.It is difficult to completely degrade it with traditional technology.If not treated and prevented in time,these pollutants will continue to accumulate in the environment and enter the ecological cycle,posing a threat to human life and health.In the face of these difficult-to-degrade pollutants,photocatalytic technology has shown a strong and effective ability to make it evolve into small molecules to harmless.Nowadays,the UV photocatalysis technology based on semiconductor Ti O₂is very mature,but its inability to use visible light is the biggest drawback.Ultraviolet light energy accounts for only 5%of natural light,and a large amount of visible light and infrared light energy cannot be used effectively.In recent years,how to effectively use visible light and infrared light in natural light sources has become the focus of many photocatalysis researchers.g-C₃N₄has become the focus of many visible light catalysts due to its unique advantages.In order to adjust the distribution of charges in g-C₃N₄and improve the catalytic efficiency,the study uses g-C₃N₄to reduce the recombination probability of photo-generated charges and increase the utilization rate of visible light by constructing two methods of typeⅡand type Z heterojunctions.This article uses the antibiotic levofloxacin,industrial dyes rhodamine B and methylene blue as target pollutants to evaluate the prepared photocatalytic materials.The main research contents are as follows:（1）The graphite-phase carbon nitride CPVC（polyvinyl chloride derivative）/g-C₃N₄（graphite-phase carbon nitride）composite photocatalyst was prepared by the combination of high temperature heat treatment and in-situ polymerization method.The different ratios of CPVC and g-C₃N₄,the different heat treatment temperatures of PVC and the photocatalytic activity at different p H were investigated,and it was determined that when the mass ratio of them is 0.001:1,the heat treatment temperature is 120℃.The prepared composite material has the best photodegradation efficiency.The mineralization test and cyclic experiment are used to explore the mineralization ability and reusable stability of the composite material,and the electron transfer path of the CPVC/g-C₃N₄type II heterojunction is determined according to the energy band analysis.The results of DRS and PL proved that loading CPVC with g-C₃N₄can form a heterostructure composite material,prolong the life of photo-generated charges and improve the ability of visible light catalytic degradation.（2）The layered g-C₃N₄was obtained after the second thermal stripping,and Ag₃PO₄（silver phosphate）was loaded on the surface of the flake g-C₃N₄by in-situ deposition method to prepare Ag₃PO₄/g-C₃N₄composite photocatalysts with different molar ratios.When the molar ratio is 0.3:1,the composite material shows the best catalytic performance for Levofloxacin,Rhodamine B and Methylene Blue.The mineralization test,cycle test,etc.show that loading Ag₃PO₄on g-C₃N₄can effectively improve the photocatalytic performance.The main active species were determined by the free radical capture experiment,and the mechanism of the Z-type heterostructure of the Ag₃PO₄/g-C₃N₄composite was proposed based on the energy band analysis,and the possible products and decomposition pathways of levofloxacin under the photocatalytic degradation effect were proposed.