Interaction mechanism between gaseous arsenic and the unburned carbon in coal-fired fly ash: A DFT combined thermodynamics study

Abstract

Based on the density functional theory (DFT) combined thermodynamics method, the flue gas arsenic forms from the coal-fired power plants were successfully confirmed at different temperature ranges, and the interaction mechanism of the fly ash unburned carbon (UBC) components on different gaseous arsenic species were also investigated. The content of trivalent arsenic (As3+) is the highest in flue gas, and its morphological distribution is significantly affected by the flue gas temperature. When the flue gas temperature is lower than 900 K, the As2O3 molecules are dominant in the trigonal bipyramid type. While when the temperature exceeds 900 K, the priority structure of As2O3 is chain type > horn type > trigonal bipyramid type in turn. This paper has verified the feasibility for the adsorption of flue gas arsenic via the unburned carbon in fly ash, and the performance of the zigzag carbon surface is always better than the armchair surface. This paper provides theoretical support for arsenic removal in coal-fired power plants, and also provides some new ideas for the secondary utilization of fly ash and the development of carbon-based arsenic removal adsorbent.