Use of XAFS Spectroscopy for Element Speciation in Environmentally Important Energy-Related Materials

Abstract

The determination of element speciation in environmentally important materials is often critical for understanding (i) the threat to human health posed by a specific element, and (ii) the means to minimize the environmental impact of an element during processing or in waste disposal after processing. In this overview, the use of X-ray Absorption Fine Structure (XAFS) spectroscopy is described for speciation determinations of specific elements in complex solid materials of importance to various environmental and energy issues, viz. coal combustion byproducts (ash), carbon-based sorbents for mercury capture from combustion flue gases, and airborne fine particulate matter (PM). Among the topics discussed are: the occurrence of hexavalent chromium and other potentially hazardous elemental oxidation states in coal combustion ash ; the role of chlorine, sulfur, etc., in the sorption of mercury from flue gases on carbon-based sorbents; and the occurrence of various elements such as sulfur, chromium, arsenic, halogens, etc., in National Institute of Standards and Technology (NIST) Urban and Diesel particulate matter standard reference materials, SRM 1648 and SRM 1650, respectively.