Study On Bismuth-titanium-based Composite Photocatalyst And Removal Of Mercury From Coal-fired Flue Gas

Since the industrial revolution,while energy has provided a huge driving force for productivity,its huge pollution has also emerged.At present,coal is still the largest primary energy source in my country,reaching more than 60%Coal emits many pollutants during the combustion process,including heavy metal mercury,and elemental mercury（Hg⁰）is difficult to remove with existing power plant technology.Therefore,how to remove Hg⁰efficiently and conveniently at this stage is the focus of current research on mercury emission reduction in coal-fired power plants.The rapid development of photocatalytic technology has had a revolutionary impact on different fields.The use of photocatalytic oxidation technology to remove mercury in flue gas has gradually become a research hotspot.This article mainly studies different bismuth-based photocatalysts loaded with oxygen-rich vacancies.Titanium dioxide can effectively remove zero-valent mercury in flue gas.Based on experiments,simulation and characterization,the mechanism of bismuth-based composite catalysts for catalytic oxidation of zero-valent mercury has been studied.In this study,a simple deposition method was used to successfully load gray particles of Ti O₂on the curd Bi₇O₉I₃to form a direct Z-type heterojunction.A series of characterizations proved the existence of Z-type heterojunction.By controlling the amount of loaded Ti O2 particles,a series of properties such as hole-charge separation efficiency,band gap,light absorption range,and specific surface area can be adjusted.And through a series of characterizations such as XPS,UV-dis,Mott-Schottky,etc.,the existence of the Z-scheme heterojunction is proved.Through the above properties,the sample BT-30 was successfully screened,and the heterojunction was successfully formed without any change in morphology,reaching a near-infrared absorption range of about 700nm,which doubled the specific surface area compared to other bismuth-based photocatalysts;under light conditions Below,the removal of mercury element reached 80.6%,which is a huge improvement compared with the original Bi₇O₉I₃,and the cycle experiment shows that this catalyst has sustainable catalysis.Based on a series of characterization and experiments,the reaction mechanism is studied and given.Based on the above-mentioned oxygen vacancy heterojunction,a new heterojunction containing two different vacancies was designed.Bi OI was first calcined at a temperature of 400 degrees,and then the calcined Bi OI and P25 were dissolved in ethanol and then calcined again.Both iodine and oxygen vacancies was obtained.Through a series of characterization methods such as XRD,SEM,ESR,EPR,etc.,it is fully proved that iodine vacancies and oxygen vacancies are successfully prepared and the two materials are combined into a heterojunction;for Bi OI_1-X/Ti O_2-Xseries The composite was tested for photocatalytic removal of mercury from flue gas,and the effect of the composite amount of Ti O_2-Xon the removal efficiency was studied.The composite amount of 10%maximizes the mercury removal efficiency,reaching 83.9%;through the analysis of the photocatalytic mechanism,Iodine vacancies,oxygen vacancies andⅡheterojunctions work together.The trinity enhances the electron-hole separation and enhances the photocatalytic ability;density functional theory（DFT）clarifies the existence of vacancies on the band gap response and its photocatalytic mechanism.