Density Functional Theory Study on Mechanism of Mercury Removal by CeO₂ Modified Activated Carbon

• Main Authors: Li Zhao, Yang-wen Wu, Jian Han, Han-xiao Wang, Ding-jia Liu, Qiang Lu, Yong-ping Yang
• Format: Article
• Language: English
• Published: MDPI AG 2018-10-01
• Series: Energies
• Subjects: flue gas mercury removal; activated carbon sorbent; CeO₂ doping; density functional theory(DFT) calculations
• Online Access: https://www.mdpi.com/1996-1073/11/11/2872
• ISSN: 1996-1073

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.