Effect of Halide Impregnation on Elemental Mercury Removal of Activated Carbons

Activated carbons (ACs) were impregnated with potassium halides (KX) to enhance the removal efficiency of elemental mercury (Hg⁰). In this work, the impregnation effect of potassium bromide (KBr) and potassium iodine (KI) were investigated. The surface properties of KX-ACs were determined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The pore structures and total pore volumes of the KX-ACs were analyzed using the N₂ /77 K adsorption isotherms. The Hg⁰ removal efficiency of KBr-ACs and KI-ACs was studied under simulated flue gas conditions. The effects of KI and KBr loading, adsorption temperature, and flue gas components on Hg⁰ removal efficiency were also investigated. The results showed that the Hg⁰ removal efficiency of the ACs was significantly enhanced by KI or KBr impregnation, and KI-ACs showed higher Hg⁰ removal efficiency than KBr-ACs under the same conditions. An increase in KI or KBr loading and higher adsorption temperatures improved the Hg⁰ removal efficiency, indicating that chemisorption occurred due to the reaction between X⁻ and Hg⁰. The lower extent of Hg⁰ removal exhibited by the KBr-ACs than by the KI-ACs was due to the difficulty of Br₂ formation on the surfaces.