Elemental Mercury Oxidation and Its Resultant Oxidized Mercury Adsorption by Cupric Chloride-Impregnated Carbon Sorbent

The performance of mercury sorbents has been tested at bench and pilot levels to reduce mercury emissions from coal-fired power plants. Among the sorbents, raw activated carbon has been extensively studied and has shown the capability to adsorb elemental mercury (Hg0) in the presence of other gaseous compounds such as hydrogen chloride (HCl). While the performance of chemically treated activated carbons in Hg adsorption has been examined in these laboratory and field studies, and the kinetic models of Hg adsorption onto raw activated carbon have been reported in several studies, very few studies are found to investigate the kinetics and mechanisms for Hg0 oxidation and adsorption by chemically treated carbon sorbents.

The performance of cupric chloride-impregnated carbon sorbent has been reported in our previous publications in comparison with brominated activated carbon. In this study, a possible mechanism of elemental mercury oxidation with cupric chloride and its resultant oxidized mercury adsorption onto the carbon surface will be introduced and suggested. It is speculated that cupric chloride works as an oxidation catalyst in the presence of HCl vapor (as low as 5 ppmv), and its resultant oxidized mercury is re-adsorbed onto available carbon surfaces. The oxidation state of copper species and the identification of the resultant oxidized mercury are being investigated by X-ray absorption fine structure spectroscopy, and the results will be presented. In addition, adsorption characteristics of the resultant oxidized mercury obtained in the authors' fixed-bed and entrained-flow reactors will be presented and discussed.