Mechanism of Hg removal by gaseous advanced oxidation process with Fe3O4 and H2O2
(2.School of Chemistry and Materials Science, Nanjing Normal University, Nanjing, Jiangsu, China 210023)
(3.State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan, Hubei, China 430074)
【Abstract】The decomposition properties of H2O2 molecule over Fe3O4 (111), (110), and (001) surfaces were systematically investigated by using density functional theory (DFT) calculations. The Hg adsorption and oxidation mechanisms over H2O2/Fe3O4 system were studied. The binding energies, optimized geometries, Mulliken population, and molecular orbital analysis of partial density of states (PDOS) between Hg and H2O2/Fe3O4 surfaces were proposed. The most favored configurations of H2O2 decomposition, which were associated with the generation mechanism of OH groups, as well as the intermediates of Hg species were discussed. The results showed that OH radicals were more likely produced on Fe3O4 (111), (001) A, and (110) A surfaces. The oxidative activityies of OH produced on different surfaces varied a lot. In addition, Mulliken charge population revealed Hg0 oxidation when the systems were in equilibrium because a large number of electrons transferred from Hg0 to the surface hydroxyl. The calculated binding energies suggested that the process of HO–Hg–OH and Hg–OH generation were exothermic on Fe3O4 surface with H2O2. The desorption analysis showed that HO–Hg–OH and Hg–OH intermediates had a lower desorption energy when they detached from the surface.
【Keywords】 mercury; oxidation; density functional theory; radical; surface;
 DAVID K, MILENA H, NICOLA P, et al. Contribution of contaminated sites to the global mercury budget [J]. Environ. Res., 2013, 125: 160–170.
 ZHANG X, SHEN B, SHEN F, et al. The behavior of the manganesecerium loaded metal-organic framework in elemental mercury and NO removal from flue gas [J]. Chem. Eng. J., 2017, 326: 551–560.
 XU Y, ZHONG Q, LIU X. Elemental mercury oxidation and adsorption on magnesite powder modified by Mn at low temperature [J]. J. Hazard. Mater., 2015, 283: 252–259.
 ZHAO Y, MA X, XU P, et al. Elemental mercury removal from flue gas by CoFe2O4 catalyzed peroxymonosulfate [J]. J. Hazard. Mater., 2018, 341: 228–237.
 ZHENG J, OU J, MO Z, et al. Mercury emission inventory and its spatial characteristics in the pearl river delta region, China [J]. Sci. Total Environ., 2011, 412: 214–222.
 TAN Z Q, QIU J R, SU S, et al. Study on the mercury removal mechanism of adsorbents [J]. J. Eng. Therm., 2012, 33 (2): 343–347 (in Chinese).
 LI H, ZHU L, WU S, et al. Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere [J]. Int. J. Coal Geol., 2017, 170: 69–76.
 XU H, QU Z, ZONG C, et al. Catalytic oxidation and adsorption of Hg0 over low-temperature NH3-SCR LaMnO3 perovskite oxide from flue gas [J]. Appl. Catal. B, 2016, 186: 30–40.
 LI H, ZHANG W, WANG J, et al. Coexistence of enhanced Hg0 oxidation and induced Hg2+ reduction on CuO/TiO2 catalyst in the presence of NO and NH3 [J]. Chem. Eng. J., 2017, 330: 1248–1254.
 LI H, WU S, WU C, et al. SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst [J]. Environ. Sci. Technol., 2015, 49 (12): 7373–7379.
 LI C F, DUAN Y F, TANG H J, et al. Mercury selective adsorption characteristics and SO2 poison performance on CaO [J]. CIESC Journal, 2017, 68 (9): 3565–3572 (in Chinese).
 HE D, WONG C E, TANG W, et al. Faradaic reactions in water desalination by batch-mode capacitive deionization [J]. Environ. Sci. Technol., 2016, 3 (5): 222–226.
 HAO R, ZHAO Y, YUAN B, et al. Establishment of a novel advanced oxidation process for economical and effective removal of SO2 and NO [J]. J. Hazard. Mater., 2016, 318: 224–232.
 MICOLI L, BAGNASCO G, TURCO M, et al. Vapour phase H2O2 decomposition on Mn based monolithic catalysts synthesized by innovative procedures [J]. Appl. Catal. B, 2013, 140/141: 516–522.
 DING J, ZHONG Q, ZHANG S, et al. Simultaneous removal of NOx and SO2 from coal-fired flue gas by catalytic oxidation-removal process with H2O2 [J]. Chem. Eng. J., 2014, 243: 176–182.
 LIU Y, YUSUF G A. A review on removal of elemental mercury from flue gas using advanced oxidation process: chemistry and process [J]. Chem. Eng. Res. Des., 2016, 112: 199–250.
 ZHOU C, SUN L, ZHANG A, et al. Fe3−xCuxO4 as highly active heterogeneous Fenton-like catalysts toward elemental mercury removal [J]. Chemosphere, 2015, 125: 16–24.
 XU Y, CAO L M, SUN W, et al. In-situ catalytic oxidation of Hg0via a gas diffusion electrode [J]. Chem. Eng. J., 2017, 310: 170–178.
 HAO R, ZHAO Y. Macrokinetics of NO oxidation by vaporized H2O2 association with ultraviolet light [J]. Energy Fuels, 2016, 30: 2365–2372.
 FARIBA S, ALI R, ABDOLHOSSAIN M, et al. Green oxidation of alcohols by using hydrogen peroxide in water in the presence of magnetic Fe3O4 nanoparticles as recoverable catalyst [J]. Green Chem. Lett. Rev., 2014, 7 (3): 257–264.
 ZHOU C S, SUN L S, ZHANG A C, et al. Catalytic removal of Hg0 in flue gas by heterogeneous Fenton-like catalysts [J]. CIESC Journal, 2015, 66 (4): 1324–1330 (in Chinese).
 HUNG C M, CHEN C W, JHUANG Y Z, et al. Fe3O4 magnetic nanoparticles: characterization and performance exemplified by the degradation of methylene blue in the presence of persulfate [J]. J. Adv. Oxid. Technol., 2016, 19 (1): 43–51.
 JUNGHYUN N, OSMAN I O, SAADULLAH G A, et al. Magnetite Fe3O4 (111) surfaces: impact of defects on structure, stability, and electronic properties [J]. Chem. Mater., 2015, 27 (17): 5856–5867.
 CHEN L, NI G, HAN B, et al. Mechanism of water gas shift reaction on Fe3O4 (111) surface [J]. Acta Chimica Sinica, 2011, 69 (4): 393–398 (in Chinese).
 YANG T, WEN X, REN J, et al. Surface structures of Fe3O4 (111), (110), and (001): a density functional theory study [J]. J. Fuel Chem. Technol., 2010, 38 (1): 121–128.
 HU X H. Mechanism study of hydroxyl radical generation from ozone catalyzed by metal oxide [D]. Harbin: Harbin Institute of Technology, 2013 (in Chinese).
 PAYNE M C, ALLAN D C, ARIAS T A, et al. Iterative minimization echniques for ab initio total-energy calculations: molecular dynamics and conjugate gradients [J]. Rev. Mod. Phys., 1992, 64 (4): 1045–1097.
 PERDEW J P, CHEVARY J A, VOSKO S H, et al. Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation [J]. Phys. Rev. B, 1992, 46: 6671–6687.
 LI X, PAIER J. Adsorption of water on the Fe3O4 (111) surface: structures, stabilities, and vibrational properties studied by density functional theory [J]. J. Phys. Chem. C, 2016, 120 (2): 1056–1065.
 ZHOU C, ZHANG Q, CHEN L, et al. Density functional theory study of water dissociative chemisorption on the Fe3O4 (111) surface [J]. J. Phys. Chem. C, 2010, 114: 21405–21410.
 SOMMAR J, GARDFELDT K, DAN S, et al. A kinetic study of the gas-phase reaction between the hydroxyl radical and atomic mercury [J]. Atmos. Environ., 2001, 35 (17): 3049–3054.
 GUO P, GUO X, ZHENG C G. Roles of γ-Fe2O3 in fly ash for mercury removal: results of density functional theory study [J]. Appl. Surf. Sci., 2010, 256: 6991–6996.