Fundamental Mechanisms of Mercury Removal by FeCl3- and CuCl2-Impregnated Activated Carbons: Experimental and First-Principles Study

Experimental and first-principles studies were conducted to understand the adsorption mechanism of elemental mercury on FeCl 3 - and CuCl 2 -impregnated activated carbons. Activated carbon was impregnated with either FeCl 3 or CuCl 2, and their adsorption of elemental mercury was evaluated using a laboratory-scale fixed-bed system. The fixed-bed tests were carried out by injecting only nitrogen gas to investigate the interaction between mercury and the chemical compound impregnated on the activated carbon. The test temperature was 140 °C to simulate the temperature in a particulate matter control device of full-scale facilities, such as coal-fired power plants and waste incinerators. Based on the results, CuCl 2 -impregnated activated carbons showed much higher adsorption efficiencies for elemental mercury than both activated carbons and FeCl 3 -impregnated activated carbons. Density functional theory (DFT) calculations revealed that the mercury adsorbates were adsorbed more strongly on the CuCl 2 (110) surface than on the FeCl 3 (001) surface. Electronic property analyses revealed that the CuCl 2 surface was more efficient as a mercury removal adsorbent because more electrons were shared between Hg- and Cu-influenced Cl bonds than those between Hg- and Fe-influenced Cl bonds, which resulted in the stronger Hg adsorption of the former.