Effect of Temperature and Acid Gases on Elemental Mercury Removal by a Ce–Bi-Doped Cobalt-Based Adsorbent under Simulated Flue Gas Conditions

The complex conditions of coal-fired flue gas, particularly temperature fluctuations and the presence of acid gases, pose significant challenges to elemental mercury (Hg0) removal. To address these issues, a Ce-Bi-doped cobalt-based (Ce–Bi–Co) adsorbent was synthesized and evaluated for Hg0 removal from simulated coal-fired flue gas. The adsorbent exhibited favorable Hg0 removal performance in the low-temperature range of 50–150 °C. The effects of typical flue-gas components, including O2, HCl, and SO2, were further examined in the fixed-bed reaction system. O2 promoted Hg0 oxidation by continuously replenishing surface active oxygen, while HCl enhanced Hg0 removal through the formation of reactive chlorine species. Notably, low concentrations of SO2 promoted Hg0 removal, whereas relatively high SO2 concentrations inhibited the performance due to competitive adsorption and the accumulation of sulfur-containing species. Comprehensive characterizations indicated that the doping of Ce and Bi modifies the surface structure and significantly enriches the chemisorbed oxygen, which directly facilitates the catalytic oxidation of Hg0. XPS analysis showed that chemisorbed oxygen directly participated in Hg0 oxidation, while Co3+ and the Ce4+/Ce3+ contributed to the surface redox reactions. This study provides practical insights for the application of modified Co-based materials for mercury emission control under coal-fired flue gas.