Theoretical Study on Hg0Adsorption and Oxidation Mechanisms over CuCl2-Impregnated Carbonaceous Material Surface

CuCl2-modified carbonaceous materials have been regarded as a kind of mercury sorbent, but the Hg0reaction mechanism over CuCl2-impregnated sorbent surface is still unclear. In this work, the binding mechanism of Hg0on CuCl2-impregnated carbonaceous material surface was investigated using hybrid density functional theory (DFT). The results indicate that the dissociation mechanism is responsible for CuCl2adsorption over carbonaceous material sorbent surface. The active chlorine species generated from CuCl2adsorption can significantly enhance mercury adsorption over carbonaceous material sorbent surface. Hg0adsorption over CuCl2-impregnated carbonaceous material surface is dominated by a chemisorption mechanism. Surface Cl and C atoms are identified as the active sites for Hg0adsorption on CuCl2-impregnated carbonaceous material surface. CuCl2plays an important role in mercury adsorption on CuCl2-impregnated carbonaceous materials. CuCl2includes the following roles: (1) CuCl2can increase the reactivity of its neighbor adsorption sites on carbonaceous material surface; (2) CuCl2can provide additional active sites for Hg0adsorption; (3) CuCl2can provide Cl atoms for the oxidation of Hg0into HgCl. Heterogeneous mercury oxidation over CuCl2-impregnated carbonaceous material surface includes four steps: Hg0adsorption, Cl migration, HgCl2formation, and HgCl2desorption. HgCl2formation is identified as the rate-limiting step of Hg0oxidation on CuCl2-impregnated carbonaceous material surface.