Molecular-level insights into efficient immobilization of gas-phase elemental mercury by zinc selenide

Abstract

Abstract Due to its low cost, rich resource reserve, and high affinity for gas-phase mercury, zinc selenide has been investigated as a promising sorbent to control mercury emission. In order to gain molecular level insights into the adsorption mechanism, density functional theory (DFT) calculations were applied to the process of mercury adsorption on the (1\xa01\xa00) surface of ZnSe. Our results indicated that chemical adsorption played a crucial role in the Hg0 adsorption on the ZnSe (1\xa01\xa00) surface. Mercury atoms interacted energetically with surface Zn atoms through the interactions between atomic orbitals. The proposed process of transformation of Hg to HgSe can be described in three steps: i.e., Hg0\xa0→\xa0Hg (ads)\xa0→\xa0HgSe (ads)\xa0→\xa0HgSe. The effects of SO2, H2O, and HCl on the adsorption of Hg0 on the surface of ZnSe were also investigated. SO2, H2O, and HCl are able to be chemisorbed on the surface of ZnSe (1\xa01\xa00) with the highest binding energies of −43.58\xa0kJ/mol, −72.23\xa0kJ/mol, −52.93\xa0kJ/mol, respectively. Moreover, SO2 shows a dual effect on Hg0 binding, while H2O and HCl may suppress Hg0 adsorption on the ZnSe (1\xa01\xa00) surface. Theoretical study suggested that ZnSe sorbent has an excellent potential for the efficient removal of gas-phase mercury.