Abstract
Doping of CeO2 on activated carbon (AC) can promote its performance for mercury abatement in flue gas, while the Hg0 removal mechanism on the AC surface has been rarely reported. In this research, density functional theory (DFT) calculations were implemented to unveil the mechanism of mercury removal on plain AC and CeO2 modified AC (CeO2-AC) sorbents. Calculation results indicate that Hg0, HCl, HgCl and HgCl2 are all chemisorbed on the adsorbent. Strong interaction and charge transfer are shown by partial density of states (PDOS) analysis of the Hg0 adsorption configuration. HCl, HgCl and HgCl2 can be dissociatively adsorbed on the AC model and subsequently generate HgCl or HgCl2 released to the gas phase. The adsorption energies of HgCl and HgCl2 on the CeO2-AC model are relatively high, indicating a great capacity for removing HgCl and HgCl2 in flue gas. DFT calculations suggest that AC sorbents exhibit a certain catalytic effect on mercury oxidation, the doping of CeO2 enhances the catalytic ability of Hg0 oxidation on the AC surface and the reactions follow the Langmuir–Hinshelwood mechanism.
Highlights
Mercury pollution has attracted widespread attention due to the toxic effect, mobility, persistence, and bioaccumulation [1]
density functional theory (DFT) calculations suggest that activated carbon (AC) sorbents exhibit a certain catalytic effect on mercury oxidation, the doping of CeO2 enhances the catalytic ability of Hg0 oxidation on the AC surface and the reactions follow the Langmuir–Hinshelwood mechanism
DFT calculations were implemented in this paper to study the Hg0 adsorption and oxidation mechanism in coal-fired flue gas on a plain AC surface and CeO2 -AC surface
Summary
Mercury pollution has attracted widespread attention due to the toxic effect, mobility, persistence, and bioaccumulation [1]. Hg2+ and HgP can be removed by existing pollutant control equipment in coal-fired power stations, while Hg0 is hard to control since it is chemically stable and insoluble in water [8,9,10]. Hg0 removal from flue gas is a research hotspot for mercury pollution control in coal-fired power stations. Modification of carbon based sorbents can enhance the adsorption capacity for Hg0 in flue gas and reduce the consumption of AC sorbents, saving a large amount of operating expenses for coal-fired power plants. Experimental studies have shown that the doping of metal oxides such as CeO2 can change the physical and chemical conditions on the AC surface and significantly enhance its mercury removal efficiency in coal-fired flue gas [17,18,19,20,21,22,23]. To better clarify the promotion effect of CeO2 doping, a series of calculations was performed on the plain AC surface as a comparison
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