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

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 SO32/SO42 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 towardHg(O) 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. (C) 2016 Published by Elsevier Ltd.