XAFS investigation of mercury sorption on carbon-based and other sorbent materials

The sorption of mercury from simulated coal combustion hue gases on coal-derived chars, activated carbons, and zeolites has been examined using mercury L-III XAFS spectroscopy. The energy difference between the two inflection points (IPD) in the mercury XANES spectra has been shown to be a sensitive indicator of the local structure around the mercury adsorbed on the sorbent The value of the IPD appears to reflect the form of mercury added to the flue gas and to be sensitive to acidic gaseous species such as HCI and H2SO4 that may be present in the flue gas, whether from addition to the flue gas or from the sulfur and chlorine in the coal. The data suggest that well-defined mercury species are not formed on carbon-based sorbents, but rather the structure and chemistry of the sorbed mercury species reflect the different anionic species present in the flue gas, as well as any activating element on the sorbent itself.