Adsorption behavior of mercuric oxide clusters on activated carbon and the effect of SO2 on this adsorption: a theoretical investigation.

The release of mercury (Hg) species from coal-fired power plants has attracted increasing concern, and the development of an efficient and economical method to control Hg species emission from such plants is urgently required. Activated carbon is a compelling sorbent for the elimination of mercury species from flue gas, but the adsorption mechanism of mercuric oxide clusters on carbonaceous materials is still unclear. Therefore, the adsorption characteristics of mercuric oxide clusters on activated carbon were investigated systematically utilizing density functional theory in this work. It was found that mercuric oxide clusters are chemically adsorbed on activated carbon, and that the pre-adsorption of SO2 on the activated carbon leads to complicated mercuric oxide cluster adsorption behavior due to an irregular distribution of the electrostatic potential on the surface of the carbonaceous material. Thermodynamic analysis indicated that the adsorption energy of SO2 on activated carbon is lower than that of mercuric oxide clusters in the temperature range 298.15-1000 K. Competitive adsorption analysis suggested that mercuric oxide clusters are at least 108.11 times more likely than SO2 to be adsorbed on activated carbon. Graphical abstract Competitive adsorption between SO2 and HgO clusters on activated carbon surface in flue gas of coal-fired power plants.