Mechanistic studies of mercury adsorption and oxidation by oxygen over spinel-type MnFe2O4.
MnFe2O4has been regarded as a very promising sorbent for mercury emission control in coal-fired power plants because of its high adsorption capacity, magnetic, recyclable and regenerable properties. First-principle calculations based on density functional theory (DFT) were used to elucidate the mercury adsorption and oxidation mechanisms on MnFe2O4surface. DFT calculations show that Mn-terminated MnFe2O4(1 0 0) surface is much more stable than Fe-terminated surface. Hg0is physically adsorbed on Fe-terminated MnFe2O4(1 0 0) surface. Hg0adsorption on Mn-terminated MnFe2O4(1 0 0) surface is a chemisorption process. The partial density of states (PDOS) analysis indicates that Hg atom interacts strongly with surface Mn atoms through the orbital hybridization. HgO is adsorbed on the MnFe2O4surface in a chemical adsorption manner. The small HOMO-LUMO energy gap implies that HgO molecular shows high chemical reactivity for HgO adsorption on MnFe2O4surface. The energy barriers of Hg0oxidation by oxygen on Fe- and Mn-terminated MnFe2O4surfaces are 206.37 and 76.07kJ/mol, respectively. Mn-terminated surface is much more favorable for Hg0oxidation than Fe-terminated surface. In the whole Hg0oxidation process, the reaction between adsorbed mercury and surface oxygen is the rate-determining step.
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Yingju
Y
Yang
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; Shenzhen Institute of Huazhong University of Science and Technology, Shenzhen 518000, China. Electronic address: liujing27@mail.hust.edu.cn.
Jing
J
Liu
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Bingkai
B
Zhang
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Feng
F
Liu
Density functional theory; Mercury adsorption; MnFe(2)O(4); Oxidation mechanism