Sequential Extraction Study of Stability of Adsorbed Mercury in Chemically Modified Activated Carbons

8 ABSTRACT: Activated carbons chemically modified with sulfur and bromine are 9 known for their greater effectiveness in capturing vapor Hg from coal combustion 10 and other industrial flue gases. The stability of captured Hg in spent activated 11 carbons determines the final fate ofHgand is critical to devising Hg control strategy. 12 However, it remains a subject that is largely unknown, particularly for Br-treated 13 activated carbons. Using a six-step sequential extraction procedure, this work 14 evaluated the leaching potential of Hg captured with four activated carbons, one 15 lignite-derived activated carbon, and three chemically treated with Br2, KClO3, and 16 SO2. The results demonstrated clearly the positive effect of Br- and SO2-treatment 17 on the stability of captured Hg. The Hg captured with brominated activated carbon 18 wasverystableandlikelyintheformofmercurousbromidecomplex.Sulfuraddedat 19 high temperature with SO2 was able to stabilize a majority of Hg by forming sulfide 20 andpossiblysulfonatechelate.Thepresenceofsulfatehowevermadeasmallfraction 21 ofcapturedHg(<10%)labileundermildconditions.TreatingactivatedcarbonwithKClO3lowered theoverallstabilityofcaptured 22 Hg. A positive dependence of Hg stability on Hg loading temperature was observed for the first time.