| Carbonaceous and non-carbonaceous adsorbents were prepared to evaluate the influences of their physical and chemical properties on the removal of trace amounts of Hg0 and HgCl2 from simulated coal combustion flue gases. These adsorbents include coal-derived activated carbons (CDACs), activated carbon fibers (ACFs), coal fly ash, pistachio shell char (PSC), pistachio activated carbon (PAC), and zeolite adsorbents. Selected samples were impregnated with elemental sulfur at 250–650°C to characterize the samples' properties after sulfur impregnation and to evaluate the adsorbents' Hg0 and HgCl2 equilibrium adsorption capacities. Results indicate that low-cost, high-capacity adsorbents (e.g., CDACs) can be developed from precursors containing inherent sulfur (e.g., coal). The resulting samples, without using sulfur impregnation, achieved mercury adsorption capacities up to 2500 μg/g. Sulfur impregnation increased the sulfur contents, decreased the surface areas, and strongly influenced the mercury adsorption capacities of adsorbents. Sulfur impregnation at a moderate temperature (e.g., 400°C) was shown to be superior and potentially optimal to produce effective carbonaceous adsorbents, which increased the equilibrium mercury adsorption capacities of ACF samples up to 11000 μg/g. These results suggest that the combination of suitable chemical and physical properties of adsorbents contributes to the success of mercury adsorption process. Results shown in this research also clearly indicate that the adsorption mechanism of mercury on the surface of sulfur-containing adsorbents is chemisorption. |
