Effect of characteristics of KI-impregnated activated carbon and flue gas components on Hg0 removal

Abstract The KI-impregnated activated carbon (KI-AC) was synthesized to investigate its capacity for elemental mercury (Hg 0 ) removal under the simulated flue gas. The Hg 0 removal performance is significantly promoted by KI loading. The effect of reaction temperature and activated carbon porosity on Hg 0 removal, and calculation on desorption activation energy of adsorbed mercury species were employed to identify the relationships between the physicochemical characteristics of the KI-AC and Hg 0 removal capacity. Raising the reaction temperature weakens the function of physisorption in the process of Hg 0 removal. The Brunauer-Emmett-Teller (BET) surface area and desorption activation energy of the adsorbed mercury species analyses indicate that the Hg 0 removal occurs through a combination of physisorption and chemisorption, and the chemisorption dominates the reaction. In addition, the influences of flue gas components on Hg 0 removal over KI-AC were evaluated, and the adsorption mechanisms were proposed. Oxidation of I − ion by the presence of O 2 is the substantial reason that facilitates the Hg 0 removal. The Hg 0 removal performance is promoted by the generation of SO 3 2− /SO 4 2 − and slightly frustrated by the competitive adsorption as well as consumption of I 2 molecules. Higher concentration of NO inhibits the generation of HgO products. However, the KI-AC sample remains highly active toward Hg 0 removal in the presence of NO because of the reaction with active N-containing groups. Additionally, the affinity capacities between Hg 0 and the various groups generated on the KI-AC follow the sequence: N → S-containing groups.