Density Functional Theory Study of Mercury Adsorption on CuS Surface: Effect of Typical Flue Gas Components

Copper sulfide (CuS) has been proved to be a potential alternative to traditional sorbents for control of elemental mercury (Hg-0) emissions downstream of the wet flue gas desulfurization (WFGD) systems. However, the detailed reaction mechanisms involved in Hg-0 adsorption over CuS surface are still unclear. The density functional theory was applied to investigate Hg-0 adsorption over CuS(001) surface. The results indicated that the chemisorption mechanism was responsible for Hg-0 adsorption over CuS(001) surface. The formation of Hg-S and Hg-Cu bonds was confirmed by depicting the projected densities of states profiles. The binding energies of Hg-0 suggested that the crystal surface with two sulfur terminations [labeled CuS(001)-S-2] exhibited a better Hg-0 adsorption activity than the crystal surface with copper and sulfur terminations [labeled CuS(001)-Cu/S]. Moreover, the adsorption of the flue gas components downstream of WFGD (oxygen, sulfur dioxide, and water vapor) was studied to understand the effect of the flue gas components on Hg-0 adsorption over CuS surface. The slight competitive adsorption further identified the negligible influence of oxygen, sulfur dioxide, and water vapor on Hg-0 adsorption in previous experiments.