Vapor-phase elemental mercury adsorption by activated carbon impregnated with chloride and chelating agents Original Research Article

The dynamic adsorption capacity for vapor-phase elemental mercury (Hg0) of commercially available granular activated carbon (BPL) impregnated with copper chloride (BPL-C), β-aminoanthraquinone (BPL-A), 2-(aminomethyl)pyridine (BPL-P), and 2-aminoethanethiol (BPL-T) was studied in an attempt to produce economical and effective sorbents for the control of elemental mercury emissions from combustion processes. The dynamic adsorption capacity of BPL-C was found to increase as empty bed contact time (EBCT) and chloride content increased and to decrease with an increase in operating temperature when dry nitrogen was used as a carrier gas. BPL carbon impregnated with 5 wt.% chloride exhibited a higher dynamic adsorption capacity than sulfur impregnated carbon tested previously. However, the observation of oxidized forms of mercury in the effluent from a fixed-bed adsorber under all experimental conditions used in this study indicates that the bond between adsorbed mercury and BPL-C is unstable or that the BPL-C itself lacks the thermal stability required for full-scale applications. BPL-A and BPL-T exhibited high dynamic adsorption capacities at 25°C but had much lower dynamic adsorption capacities at 140°C, while BPL-P showed very poor performance at both temperatures. Due to the high production costs, these chelating agent-impregnated carbons would likely be considerably less cost-effective for the full-scale removal of mercury from combustion flue gases than the chloride- or sulfur-impregnated carbons. Impregnation with thiol was the only promising approach that could provide effective mercury sorbents at room temperature.