The Preparation Of Fenton-like Catalysts Based On G- C₃N₄ And Their Catalytic Degradation Performance Studies In The Photo-assisted Conditions

The improvement of water environment is an important problem for human beings to solve.The main research work of this paper is that combining the photocatalytic oxidation process with heterogeneous Fenton-like oxidation process to degrade organic pollutants,such as methylene blue?MB?and rhodamine B?RhB?.These two processes have complementarity in technology to some extent.Combining the two processes can improve the degradation efficiency of organic pollutants.Through the literature research,we conducted the following three studies.In chapter 2 of this paper,the copper and carbon ring-g-C₃N₄ composite catalysts with different copper contents were prepared by the method of calcination.The photo-assisted Fenton-like catalytic activity of Cu-C-CN is obviously higher than that of g-C₃N₄ and carbon ring-g-C₃N₄ in the presence of visible light and H₂O₂ on MB degradation.3Cu-C-CN shows the best catalytic activity,and the reaction rate constant of 3Cu-C-CN is 5.5 times and 4.1 times higher than that of g-C₃N₄ and carbon ring-g-C₃N₄,respectively.The contrast experiments of different catalysts were conducted in the presence of visible light and/or H₂O₂.The results exhibit that the photo-assisted Fenton-like catalytic effect?the co-existence of visible light and H₂O₂?is higher than the sum of the corresponding phocatalytic effect?only visible light?and Fenton-like effect?only H₂O₂?,indicating that there is a synergistic effect between the photocatalytic process and the Fenton-like process.According to the literature and experimental studies,a possible reaction mechanism of Cu-C-CN in the photo-assisted Fenton-like catalytic process was proposed.Lastly,the stability and reusability of Cu-C-CN was verified by cyclic tests and the concentration of leached copper ions.In the third chapter,the Fenton-like catalyst of CoWO₄ with different weight ratio was loaded in g-C₃N₄ through the way of hydrothermal and calcination.The photo-assisted Fenton-like catalytic activity of CoWO₄/g-C₃N₄ is obviously higher than that of g-C₃N₄ and CoWO₄ in the presence of visible light and PMS on RhB degradation.9.0%CoWO₄ shows the best catalytic activity,and the reaction rate constant is 11 times and 2 times higher than that of g-C₃N₄ and CoWO₄,respectively.The contrast experiments of different catalysts were conducted in the presence of visible light and/or PMS.The results exhibit that the photo-assisted Fenton-like catalytic effect?the co-existence of visible light and PMS?is higher than the sum of the corresponding phocatalytic effect?only visible light?and Fenton-like effect?only PMS?,indicating that there is a synergistic effect between the photocatalytic process and the Fenton-like process.According to the literature and experimental studies,a possible reaction mechanism of CoWO₄/g-C₃N₄ in the photo-assisted Fenton-like catalytic process was proposed.At last,CoWO₄/g-C₃N₄ is proved to be stable and reusable by cyclic tests.On the basis of the third chapter's research,in the fourth chapter,Co was embedded in the substrate of g-C₃N₄ in the form of coordination to prepare atomically dispersed cobalt-based catalyst.Active metal atoms were utilized to the maximum extent to improve the catalytic activity,combining the characteristics of high activity of homogeneous catalyst and easy separation of heterogeneous catalyst.The Co-g-C₃N₄composite catalysts with different cobalt mass fractions were prepared by impregnation and calcination.The photo-assisted Fenton-like catalytic activity of Co-g-C₃N₄ is obviously higher than that of g-C₃N₄ in the presence of visible light and PMS on RhB degradation.1.0%Co-g-C₃N₄ shows the best catalytic activity,and the reaction rate constant of 1.0%Co-g-C₃N₄ is 18 times higher than that of g-C₃N₄.The contrast experiments of different catalysts were conducted in the presence of visible light and/or PMS.The results exhibit that the photo-assisted Fenton-like catalytic effect?the co-existence of visible light and PMS?is higher than the sum of the corresponding phocatalytic effect?only visible light?and Fenton-like effect?only PMS?,indicating that there is a synergistic effect between the photocatalytic process and the Fenton-like process.According to the literature and experimental studies,a possible reaction mechanism of Co-g-C₃N₄ in the photo-assisted Fenton-like catalytic process was proposed.At last,the stability of Co-g-C₃N₄ was tested by cyclic tests.The combination of photocatalytic process and Fenton-like process can fill the defect of single oxidation process.The degradation efficiency of the catalysts in the photocatalytic process,Fenton-like process and the photo-assisted Fenton-like catalytic process was investigated.It was proved that there was a synergistic effect between the photocatalytic process and the Fenton-like process,accelerating the generation of more reactive species.Thus,the combined technology plays an important role in water treatment.