Removal of Gaseous Elemental Mercury by Cylindrical Activated Coke Loaded with CoO_x‑CeO₂ from Simulated Coal Combustion Flue Gas

Co–Ce mixed oxides were loaded on commercial cylindrical activated coke granules (CoCe/AC) by an impregnation method to remove gaseous elemental mercury (Hg⁰) from simulated coal combustion flue gas at low temperature (110–230 °C). Effects of the Co/Ce molar ratio in Co–Ce mixed oxides, mixed oxides loading value, reaction temperature, and flue gas components (O₂, NO, SO₂, H₂O) on Hg⁰ removal efficiency were investigated, respectively. Brunauer–Emmett–Teller analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) analysis were employed to analyze the characteristics of the samples. Results showed that up to 92.5% of Hg⁰ removal efficiency could be obtained over Co_4.5Ce₆/AC at 170 °C. The remarkably high Hg⁰ removal ability of Co_4.5Ce₆/AC mainly depended on the synergetic effect between cobalt oxide and ceria. Additionally, different with the pure N₂ condition, the existence of O₂ and NO could increase Hg⁰ removal efficiency. SO₂ exhibited an inhibitive effect on Hg⁰ removal in the absence of O₂. H₂O­(g) could slightly hinder Hg⁰ removal. The characterization results exhibited that addition of cobalt oxide led to the excellent dispersity of CeO₂ on AC. TGA and XPS analysis results revealed that the captured mercury species on the used Co_4.5Ce₆/AC mainly existed as HgO, and both lattice oxygen and chemisorption oxygen contributed to Hg⁰ oxidation. Furthermore, the mechanisms involved in Hg⁰ removal were identified.