Theoretical Studies of the NO Effect on the Mercury Adsorption Capacity of a Carbonaceous Surface

Abstract

A systematic theoretical study using the density functional theory is performed to provide a molecular-level understanding of the NO effect on the mercury adsorption on a carbonaceous surface. A six-fused benzene ring is examined to serve as a representative cluster species to model the carbonaceous surface. The edge atoms on the upper side of the models are unsaturated to simulate the active sites. All of the possible approaches in which NO is adsorbed on the edge sites of the carbonaceous surface are considered to examine their effects on Hg adsorption. The results indicate that NO adsorptions with side-on and N-down modes are thermally favorable, while the O-down mode is not energetically favorable for NO adsorption on the carbonaceous surface. The effects of NO on the Hg adsorption capacity of the carbonaceous surface are complicated, and they depend upon the concentration of NO in flue gas. A low concentration of NO promotes Hg adsorption on the carbonaceous surface, while higher concentrations of NO decrease the adsorption capacity of Hg because NO competes for the activate sites on the carbonaceous surface.