Mechanistic studies of carbocycles on elemental mercury adsorption on carbonaceous surface

Multiple-membered carbocycle (MMC) is a potential material to modify activated carbon for mercury removal in coal-fired power plants due to its unique effect on carrier properties. Density functional theory (DFT) method was utilized for the first time to reveal the effect of MMC on elemental mercury adsorption on the carbonaceous surface. The calculation results indicate that the distribution of C–C bond lengths presents two different trends due to the influence of MMC. Then, all mercury-containing models are divided into three categories based on the mercury position and adsorption energy. The adsorption energy can reach the maximum value only when the mercury is co-adsorbed by substrate surface and MMC, such as Model C(B), D(B) and I(T&B). The Mulliken charge population implies that the four-membered carbocycle is capable to repel electrons, which can be regarded as an effective tool for charge rearrangement. In addition, the magnitude of charge transfer directly determines the adsorption energy, which is reflected in the order of three categories. The partial density of state (PDOS) and HOMO-LUMO energy gap analyses show that the adsorption energy of the second and third categories increases as the number of carbon atoms on MMC increases.