The adsorption of mercury species(Hg0,HgCl and HgCl2)and catalytic oxidation of Hg0 on the metalloaded activated carbon(AC)with single Fe,Co,Ni,Cu and Zn atom have been studied using the periodic density functional theory(DFT)method.The results indicate that Hg0 interacts with metal-loaded AC surfaces via a physical adsorption mechanism,while chemisorptions are likely adsorption mechanisms for HgCl and HgCl2.The existence forms of HgCl and HgCl2 on metal-loaded AC surfaces are dissociated or molecular,which greatly depend on initial interaction modes between mercury species and surfaces.Besides,in the presence of Cl2,Hg0 is oxidized to be HgCl2 molecule on the Fe/AC surface,while dissociatively adsorbed HgCl2 is predominant on Ni/AC,Cu/AC and Zn/AC surfaces,but both molecular and dissociated HgCl2 exist on the Co/AC surface.Whats more,the kinetic results show that the oxidation energy barrier of Hg0 on the Fe/AC surface is the lowest,implying that Fe-loaded AC is a favorable heterogeneous catalyst for Hg0 oxidation from the point of view of efficiency and cost.