Adsorption of Gaseous Elemental Mercury by Ferric-Chloride-Modified Activated Carbon Under Low-Temperature Conditions

Removal efficiency of elemental mercury (Hg 0 ) over activated carbon (AC) modified with ferric chloride (FeCl 3 ) is investigated at low temperatures. The effects of impregnation concentration, reaction temperature, oxygen content, relative humidity, and hydrogen sulfide (H 2 S) on Hg 0 removal efficiency are investigated. The results indicate that the removal ability of Hg 0 can be significantly improved by the introduction of FeCl 3 . Furthermore, the FeCl 3 -modified AC exhibit the best removal efficiency toward Hg 0 when the concentration of FeCl 3 is 0.15 mol L −1 and reaction temperature is 50 °C. In addition, H 2 S shows a positive effect on Hg 0 removal, while H 2 O(g) can inhibit the removal of Hg 0 due to competitive adsorption. Fe 2 O 3 and C  Cl are generated on FeCl 3 -modified AC (with FeCl 3 impregnation concentration of 0.15 mol L −1 ) catalyst and contribute to Hg 0 removal. Moreover, Hg exists mainly in the form of mercuric chloride (HgCl 2 ) and mercuric oxide (HgO) on the surface of the samples. Finally, the removal of Hg 0 is achieved through the following two pathways: by the reaction of Hg 0 with C  Cl and reaction of Hg 0 with Fe 2 O 3 .