Preparation Of Graphitic Carbon Nitride Supported By Transition Mental Single Atom And Application Of Pollutants Degradation

Advanced oxidation processes（AOPs）have shown excellent performance in environmental remediation,which can produce highly reactive oxygen species for degradation of toxic organic pollutants into harmless mineralized salts,CO₂ and H₂O.It is a top priority to find the applicable catalyst to improve the activity and application range of AOPs for the further development of AOPs.In recent years,single-atom catalysts（SACs）have attracted the attention of researchers because they not only possess the advantage of homogeneous catalysts with utmost metal utilization and excellent catalytic activity,but also possess the advantages of heterogeneous catalysts with structure stability and easy separation.Graphite carbon nitride（g-C₃N₄）has good visible light absorption and high physicochemical stability,and a large number of N atoms which can capture highly active metal atoms.Therefore,it is widely used as a support for fixing various metal atoms to prepare SACs,including noble metal（Pt,Pd,Ag and so on）and non-noble metal（Fe,Co,Ni and so on）.In this study,Fe and Mn atoms were loaded on g-C₃N₄ to prepare SA-Fe/g-C₃N₄,SA-Mn/g-C₃N₄ and SA-Mn/NG by different heating procedures,respectively.X-ray photoelectron spectroscopy（XPS）,Energy dispersive X-ray spectroscopy（EDX）and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy（AC HAADF-STEM）were used to characterize the catalysts.Bisphenol A（BPA）,tetrabromobisphenol A（TBBPA）and sulfamethoxazole（SMX）were applied to test the performance of catalysts,respectively.The main content of this project includes the following three aspects:（1）Study on the activation of hydrogen peroxide（H₂O₂）by SA-Fe/g-C₃N₄ to degrade BPA in visible lightThe precursors（PEI-MCA）were prepared by adding a certain amount of cyanuric acid（CA）,polyethyleneimine（PEI）and melamine（M）was dissolved in deionized water,the mixture was filtered and dried with a vacuum drying.For the preparation of SA-Fe/g-C₃N₄,hemin was dissolved in 4～5 m L alcohol,then the PEI-MCA was mixed with the above solution and ground into fine powder.SA-Fe/g-C₃N₄ powder was obtained at 550^°C in tube furnace.The g-C₃N₄ was obtained from the PEI-MCA in the same calcination method,and used as contrast material.The ability of g-C₃N₄ and SA-Fe/g-C₃N₄ was compared by activating H₂O₂to remove BPA in visible light.The results of the test indicated that the degradation capacity of SA-Fe/g-C₃N₄ was significantly improved.The optimum conditions for the degradation of BPA by SA-Fe/g-C₃N₄ were found to be weak acid,the concentration of H₂O₂ was 80 mmol/L,and the catalyst concentration was 0.1 g/L.（2）The ability of SA-Mn/g-C₃N₄ activated permonosulfate（PMS）to degrade TBBPA in visible lightThe PEI-MCA were obtained via adding a certain amount of CA,PEI and M in deionized water,the mixture was filtered and dried with a vacuum drying.For the preparation of SA-Mn/g-C₃N₄,meso-tetrakis（4-chlorophenyl）porphyrin-Mn（III）was dissolved in 4～5 m L alcohol,then the PEI-MCA was mixed with the above solution and ground into fine powder.The powder mixture was subjected to carbonization550^°C in tube furnace.The g-C₃N₄ obtained from the PEI-MCA in the same calcination method,and used as a contrast material.The ability of g-C₃N₄ and SA-Mn/g-C₃N₄ was compared by activating PMS to remove TBBPA in visible light.The results of the test indicated that the degradation capacity of SA-Mn/g-C₃N₄ was significantly improved.Through experiments,it was found that the optimal condition for the degradation of TBBPA by SA-Mn/g-C₃N₄ was pH=10.0,and the dose of SA-Mn/g-C₃N₄ was 0.1 g/L,the concentration of PMS was 0.2 g/L.（3）The study on SA-Mn/NG activated persulfate（PS）to degrade SMXThe preparation method of the SA-Mn/NG was same as the preparation method of SA-Mn/g-C₃N₄ mentioned above,except the calcination temperature of the mixture of meso-tetrakis（4-chlorophenyl）porphyrin-Mn（III）and PEI-MAC was 700℃way of precursors of heated to 550℃according to the same heating procedure,and then calcined at 700℃to obtain.NG obtained from the precursors in the same calcination method,and used as a contrast material.The ability of NG and SA-Mn/NG was compared for activating PS to remove SMX,the results showed that the effect of SA-Mn/NG for removing SMX was more excellent.The best condition of SA-Mn/NG degrading SMX is pH=9.0,SA-Mn/NG concentration is 0.1 g/L,PS concentration is0.2 g/L.Compared with SA-Mn/g-C₃N₄,the ability of SA-Mn/NG was not affected by light.