Manganese,Cobalt And Copper Modified Carbon Nitride Nanosheets To Control Mercury Emissions From Coal-Fired Flue Gas

Coal-fired power generation is the main direction of China's coal consumption,and the clean development of coal power is the top priority of current coal-fired power plants.As one of the most harmful pollutants produced by the combustion of coal,heavy metal mercury is becoming more and more urgent,and it is urgent to develop effective mercury emission technology for coal-fired power plants.As a new type of carbon-based polymer,carbon nitride material has attracted attention and research in the control of mercury in flue gas due to its abundant sources,convenient preparation,strong structural stability,and unique electronic structure.In this paper,graphitic carbon nitride nanosheets with higher surface area were prepared by secondary thermal etching,which reduced the dimensions of graphitic carbon nitride and improved the pore structure.The prepared carbon nitride nanosheets were doped with Mn,Co,Cu metal oxides from high to low oxidation activity in order.The synthesized samples were characterized by XRD,SEM,TEM,FT-IR and XPS to study the physical and chemical characteristics of the samples,and fixed bed adsorption experiments in simulated flue gas were carried out.MnO₂ was successfully supported on g-C₃N₄ nanosheet materials by impregnation method and calcination method.The samples before and after the reaction were characterized and analyzed to study the mechanism.Studies have shown that the removal efficiency of MnO₂/g-C₃N₄ can reach 99% when the MnO₂ content is 10wt% and the reaction temperature is 120?.It has a minimum mercury removal efficiency of 96.3% in the range of 120-240?.Through the exploration of MnO₂ modification,Co₃O₄ and CuO with less catalytic activity were further selected as modifiers,and then Co₃O₄/g-C₃N₄ and CuO/g-C₃N₄ modified carbonitride nanocomposites were successfully synthesized.The modification of Co₃O₄ and CuO both improved the Hg0 removal performance of g-C₃N₄ nanosheets.Among them,Co₃O₄/g-C₃N₄ samples with a Co₃O₄ mass content of 12wt% can reach nearly 100% mercury removal efficiency when the reaction temperature is 120-240?.CuO/g-C₃N₄ can form CuO particles with suitable particle size when the material synthesis temperature is 200?.It is obviously helpful for improving the performance of composite materials.It has good performance in the reaction temperature range of 40-240?,and the mercury removal efficiency can reach nearly 100% when the reaction temperature is 200?.Through a series of characterization analysis and experimental research.It was found that in the MnO₂/g-C₃N₄,Co₃O₄/g-C₃N₄ and CuO/g-C₃N₄ composites,no matter whether the redox ability of the metal oxide is strong or not,the Mott-Schottky effect,can significantly improve the mercury removal performance of carbon nitride nanosheet materials.The mercury removal mechanism of metal oxide modified carbon nitride nanosheet materials is closely related to chemisorbed oxygen and metal oxide lattice oxygen on the surface of the material.