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

Abstract

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 Hg0 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 Hg0 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 Hg0. Meanwhile, the oxygen-containing functional groups were also considered to research the influence on mercury adsorption with the defective surface. The adsorption of Hg0 on defective carbonaceous surfaces is associated with stable chemisorption, and surface defects can significantly improve the adsorption energy of Hg0. This theoretical study provides theoretical guidance for the development of mercury removal technology with carbon materials in the coal-fired power plant.