Cite this article: Tsai, C.Y., Chiu, C.H., Chuang, M.W. and Hsi, H.C. (2017). Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas.
Aerosol Air Qual. Res.
17: 1637-1648. https://doi.org/10.4209/aaqr.2016.10.0435
HCl pretreatment and CuCl2 impregnation caused changes in carbon properties.
Both oxygen and CuCl2 groups enhanced Hg0 adsorption.
Surface area/functionality, and flue gas components affect Hg0 adsorption.
Hg0 adsorption on CuCl2-treated adsorbents appeared to occur in bimolecular form.
The impregnated functionality enhances Hg0 adsorption equilibrium not kinetics.
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.
Keywords: Mercury; Adsorbent; Impregnation; CuCl2; Coal-combustion flue gas