Preparation Of Graphite Phase Carbon Nirtide Modified Photocatalyst And Its Photocatalytic Degradation Of Pollutants In Water

In the field of photocatalytic degradation of pollutant wastewater,the design,development and synthesis of novel composite photocatalytic materials with strong visible light response and excellent photocatalytic performance has become a hot research topic.As a typical semiconductor photocatalyst,g-C₃N₄ has been one of the most widely studied photocatalysts in this field because of its unique electronic structure and chemical stability,its absorption band response to the visible region,and its stable structure and excellent reusability.However,g-C₃N₄ has the disadvantages of wide band gap,small specific surface area and few active sites,resulting in slow separation rate of photogenerated electron-hole pair,which is limited in practical application.Therefore,it is of great practical significance to search for efficient and stable modification methods of g-C₃N₄ to prepare and synthesize new photocatalysts with excellent performance and high stability.In this paper,an efficient and stable modification method of g-C₃N₄ was discussed.Two new efficient visible light composite photocatalysts were prepared and synthesized.The catalytic activity and stability of the new composite catalyst in the photocatalytic degradation of pollutant wastewater were systematically studied.The main research contents are as follows:A series of Bi/Ce/g-C₃N₄ composite photocatalysts with different doping amounts were prepared by direct calcination method using the modification method of metal elements co-doping,and the structure,composition,morphology and performance of the catalysts were fully characterized by a series of characterization.Due to the plasmonic resonance effect of Bi and the role of Ce as an electron trapping agent,the introduction of Bi and Ce greatly inhibits the recombination of carriers,and the Bi/Ce/g-C₃N₄ composite photocatalyst has an efficient photogenerated carrier separation rate.The photocatalytic degradation of Rhodamine B and sulfamethoxazole by Bi/Ce/g-C₃N₄ composite catalyst showed that the photocatalytic performance of Bi/Ce/g-C₃N₄ catalyst was better than that of single component catalyst,and had good stability.Under the optimal experimental conditions,the degradation effects of 3Bi/Ce/g-C₃N₄ on Rh B（20min）and SMX（120 min）reached 98.3%and 70.5%,respectively.The theoretical calculation results of DFT show that the band gap width of g-C₃N₄ is reduced to 1.215 e V after Bi and Ce doping modification.Due to the inhibition of photogenerated carrier recombination by electron capture after doping modification,the band gap width is reduced and the photocatalytic activity is improved.Ecotoxicity assessment and Escherichia coli test indicated that Bi/Ce/g-C₃N₄ could be safely used for wastewater treatment.Ti₃C₂-SO₃H/g-C₃N₄ composite photocatalyst was synthesized by acid etching and sound chemistry by the modification method of constructing heterojunction.The structure,composition and morphology of the catalyst were characterized by XRD,FT-IR,XPS,SEM,UV-vis DRS and PL.The photocatalytic activity of the catalyst was evaluated by photocatalytic degradation of tetracycline,and the main active components were studied.Compared with pure g-C₃N₄,Ti₃C₂-SO₃H/g-C₃N₄ composite photocatalyst showed higher photocatalytic activity,where 10 wt%Ti₃C₂-SO₃H/g-C₃N₄ catalyst concentration was 0.6 g/L,the degradation efficiency of TC reached75.42%.It is 1.51 times that of pure g-C₃N₄,and its activity is almost unchanged after five repeated cycles.The mechanism of enhancing activity of Ti₃C₂-SO₃H/g-C₃N₄ composite photocatalyst is mainly due to the synergistic effect of Ti₃C₂-SO₃H and g-C₃N₄.Ti₃C₂-SO₃H doped with g-C₃N₄formed heterojunction,which enhanced its response to visible light and inhibited the recombination of photoelectron hole pairs,resulting in the enhancement of the photocatalyst activity of Ti₃C₂-SO₃H/g-C₃N₄ composite catalyst.In addition,the ecotoxicity assessment of tetracycline and its intermediates showed that the acute and chronic toxicity of tetracycline photodegradation to fish,water fleas and green algae was gradually reduced.