A comprehensive exploration of mercury adsorption sites on the carbonaceous surface: A DFT study

Mercury pollution released from coal-fired power plants has caused worldwide concern for its toxicity, global range transportation, and bioaccumulation. Unburned carbon in fly ash is considered to be a promising adsorbent to effectively remove elemental mercury. However, the active sites of the unburned carbon for Hg-0 adsorption have not been clearly identified, which greatly hinders the development of effective adsorbents. To reveal the adsorption sites of the carbonaceous surface, the adsorption process of Hg-0 on different carbonaceous surfaces was systematically investigated through density functional theory. The Mayer bond order, Electron localization function, and Electron density difference were used to analyze the adsorption mechanism of Hg-0. Meanwhile, the oxygen-containing functional groups were also considered to research the influence on mercury adsorption with the defective surface. The adsorption of Hg-0 on defective carbonaceous surfaces is associated with stable chemisorption, and surface defects can significantly improve the adsorption energy of Hg-0. This theoretical study provides theoretical guidance for the development of mercury removal technology with carbon materials in the coal-fired power plant.