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ROLE OF HCL IN ADSORPTION OF ELEMENTAL MERCURY VAPOR BY CALCIUM-BASED SORBENTS
Citation:
Ghorishi, B., B K. Gullett*, W. Jozewicz, AND W. Kozlowski. ROLE OF HCL IN ADSORPTION OF ELEMENTAL MERCURY VAPOR BY CALCIUM-BASED SORBENTS. Presented at Mega Symposium, Atlanta, Georgia, 8/16-20/99.
Description:
The paper gives results of a study to identify active sites and surface functional groups that may contribute to the adsorption of elemental mercury (Hg?) by relatively inexpensive calcium (Ca)-based sorbents. (NOTE: Hg? capture has been mostly investigated using high-surface-area, expensive activated carbons. Previous investigations showed that hydrogen chloride (HC1) in the flue gas had a pronounced positive effect on the adsorption of Hg? by a ignite-coal-based activated carbon with high Ca content). The study investigated the formation of chlorine (C1) sites in Ca-based sorbents as well as their role and reactivity in the adsorption of Hg?. HC1-exposed calcium sulfate dihydrate (gypsum) exhibited a superior Hg? sorption capability. Crystalline water molecules on the surface of the gypsum were confirmed to contribute indirectly to Hg? uptake. These surface molecules may have adsorbed HC1 through hydrogen bond formation between an oxygen atom of a crystalline water molecule and a hydrogen atom of an HC1 molecule. Two adjacent, physically adsorbed HC1 molecules could then trap an Hg? molecule through formation of a mercuric-chloride-like molecule. Significant correlations between C1 and Hg? uptake by gypsum were noted.