Effect of flue gas on elemental mercury removal capacity of defective carbonaceous surface: A first-principles study

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.