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J Hazard Mater. 2019 Jul 15;374:267-275. doi: 10.1016/j.jhazmat.2019.04.006. Epub 2019 Apr 3.

Inherent thermal regeneration performance of different MnO2 crystallographic structures for mercury removal.

Author information

1
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada.
2
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China. Electronic address: yfduan@seu.edu.cn.
3
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada.
4
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
5
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada; Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China. Electronic address: zhenghe.xu@ualberta.ca.

Abstract

Manganese oxides with different crystallographic structures were investigated for gas-phase elemental mercury removal. The inherent thermal regeneration performance and mechanism of α- and γ-MnO2 were studied. The manganese dioxides were found to possess a mercury removal efficiency of higher than 96% even after 120 min mercury exposure except for β-MnO2 which removed much less mercury than Mn2O3. The α-MnO2 was found to have a higher recyclability of mercury capture and better durability for regeneration than γ-MnO2. During the first 1 h of exposure, α-MnO2 showed an excellent mercury capacity of 128 μg/g over 5 regeneration cycles. While for γ-MnO2, the mercury capacity of the fifth cycle was reduced to 68.74 μg/g, which is much lower than 131.42 μg/g for the first cycle. The microstructure of α-MnO2 was maintained throughout regeneration cycles due to its capability to retain lattice oxygen. In comparison, γ-MnO2 experienced reconstruction and phase transformation induced by oxygen vacancies due to lattice oxygen loss during regeneration process, leading to a degradation in mercury capture. The α-MnO2 oriented composite was found to be better developed into a regenerable catalytic sorbent for mercury removal from flue gases of coal-fired power plants.

KEYWORDS:

Coal-fired power plants; Manganese oxides; Mercury removal; Oxygen loss; Regeneration performance

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