Mercury adsorption and desorption kinetics

Mercury emissions in the United States are regulated under the Clean Air Mercury Rule. Multiple mercury removal technologies have been investigated and at this time, activated carbon injection into flue gas has been considered to be an efficient and economically feasible method for the removal of elemental mercury. Also, chemical modifications to activated carbon have shown to increase its mercury sorption capacity and removal efficiency. In this study, adsorption of elemental mercury onto ferric chloride impregnated activated carbon was investigated. The results show that ferric chloride impregnated activated carbon has a higher mercury sorption capacity than raw activated carbon does. A chemisorption mechanism was proposed and confirmed based on the characterization tests of fresh and spent sorbents. A kinetic study for the regeneration of spent sorbents was also conducted. The activation energies of mercury desorption from various substrates were calculated and the corresponding mercury desorption profiles were mathematically modeled.