RESUMO
The atomic interaction between elemental mercury in the flue gas and defective carbonaceous surface is studied by the first-principles calculation. The defective carbonaceous surface is modeled by a nine-fused benzene cluster with two adjacent atomic vacancies. The results indicate that vacancies can increase the activity of their neighboring carbon atoms. However, the vacant sites present the decrease in mercury removal capacity, which is different from the behavior of the defective carbonaceous surface with only one atomic vacancy. In addition, flue gas molecules (FGMs) including CO, CO2, NO, NO2, SO2 and H2O, are examined to evaluate the influence on the mercury removal of the defective carbonaceous surface. The calculated results demonstrate that different adsorption behaviors for Hg0 occur on the defective carbonaceous surface due to the presence of FGMs. It can be found that CO may enhance the mercury removal capacity of the defective carbonaceous surface when its concentration is higher than that of Hg0. Meanwhile, SO2 presents the remarkable positive effect on the mercury removal efficiency at the vacancy. On the contrary, the presence of CO2, NO, NO2 and H2O leads to the increase in the adsorption energies of mercury on the defective carbonaceous surface.
RESUMO
The interaction of elemental mercury with defective carbonaceous clusters is investigated by the density-functional theory calculation. The defective carbonaceous cluster is represented by seven-fused benzene ring and single atomic vacancy at the surface. Also, the non-defective carbonaceous surface is employed for comparison. The defective carbonaceous cluster with chlorine is carried out to evaluate the effect of the statured carbon at the neighboring sites of vacancy on mercury adsorption. The results indicate that vacancy can promote the activity of its neighboring sites, and the defective carbonaceous cluster has much larger mercury adsorption energy than the non-defective carbonaceous cluster with and without chlorine. Cl atom can improve the activity of its neighboring sites on the non-defective carbonaceous surface, but the effect of Cl atom on mercury adsorption of vacancy is very complex, which depends on the Cl concentration. High concentration of Cl decreases the mercury adsorption because Cl competes for the active sites with mercury. Hence, we find that vacancy can be regarded as a potential functional group to improve the mercury adsorption on carbonaceous surface, but the saturated carbon at the neighboring sites of vacancy can rapidly decrease the mercury capture capacity.