Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas

ABSTRACT

In this study, the Hg⁰ adsorption equilibrium and kinetics of a coconut-shell-based activated carbon impregnated with CuCl₂ were examined with respect to their resulting physical and chemical properties. Integrating the results from N₂ adsorption isotherm at 77 K, scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and Hg⁰ adsorption experiments under N₂ and simulated coal-combustion flue gases conditions, it was found that HCl pretreatment could enhance Hg⁰ adsorption of crude activated carbon; the Hg⁰ adsorption capacities of crude and HCl-pretreated activated carbon under N₂ condition were 95.8 and 225.4 µg g^–1, respectively. Additionally, CuCl₂ impregnation further increased the adsorption capacity of crude. The Hg⁰ adsorption capacity of crude activated carbon with 8% CuCl₂ impregnation was 631.1 µg g^–1. However, the equilibrium Hg⁰ adsorption capacity decreased when Cu loading exceeded 8 wt%, suggesting that adequate forms of surface Cu, O and Cl interacting with flue gas components and Hg⁰, as well as the presence of pores with specific size ranges allowing rapid transport of the Hg molecules into the interior of the activated carbon and as energy sinker govern the overall chemisorption process. Pseudo-second-order kinetic model could best describe the adsorption behaviors of tested samples under both test conditions, indicating that Hg⁰ adsorbed on the activated carbon surface could be explained by bimolecular reaction mechanisms.