Abstract:
The mechanism of adsorption and oxidation of Hg0 by HCl on γ-Fe2O3 surface was investigated by density functional theory (DFT) calculation. The adsorption models of Hg0, HCl, HgCl and HgCl2 on γ-Fe2O3(001) surface were constructed, and the reaction mechanism of catalytic oxidation of Hg0 by HCl on γ-Fe2O3 surface was analyzed. The results illustrate that the Hg0 tends to be chemically adsorbed at Feoct site. HCl can be dissociated and adsorbed on the surface of the catalyst to form adsorbed Cl and hydroxyl groups, and promote the adsorption of Hg0. HgCl can be molecularly chemisorbed upon γ-Fe2O3(001) and act as an intermediate. HgCl2 tends to be adsorbed in parallel on the surface of γ-Fe2O3. HCl oxidizes Hg0 on γ-Fe2O3(001) following the L-H mechanism: chemically adsorbed Hg0 reacts with dissociatively adsorbed HCl. By measuring the energy distribution of the reaction path, the oxidation process of Hg0 on the surface of γ-Fe2O3 was studied. The heterogeneous oxidation of Hg0 by HCl proceeds on a two-step reaction pathway: Hg0(ads)→HgCl(ads)→HgCl2(ads).