Insight into mercury-laden activated carbon adsorbent product bonding nature by DFT calculations

[Display omitted] •The properties of the spent adsorbent product were investigated based on DFT methods.•The effects of oxygen functional groups and halogen species were considered.•The bond strength and bond polarity were characterized quantitatively. The coal-fired power plant is the main contributor to anthropogenic mercury emission in China. Adsorbent injection technology has proven to be the most promising and established strategy for controlling mercury release. The ultimate fate of mercury-loaded adsorbent product would be landfilled or reused as architecture materials. Either way, the chemical stability of mercury-containing products is important. The objective of this research is to reveal the binding nature of spent adsorbents. In particular, computational chemistry was utilized. The effects of different oxygen functional groups (carbonyl, carboxyl, lactone, and phenol) on the carbonaceous surface were considered. Furthermore, the influence of chlorine and bromine was also considered. The bond length and Mayer bond order value of chemical bonds of interest were calculated and compared to indicate their bond strength. The electron localization function (ELF) was employed to locate electron high localization regions in the product. Additionally, the Hirshfeld weighting function for decomposing bonding localized molecular orbital (LMO) to the two connected atoms compositions were utilized to characterize different chemical bonds bonding polarity quantitatively. In summary, the results are beneficial for understanding the chemical characteristics and environmental stability of used mercury removal adsorbents.