Direct speciation of chromium in coal combustion by-products by X-ray absorption fine-structure spectroscopy

Chromium X-ray absorption fine-structure (XAFS) spectroscopy has been used to determine the relative amounts of Cr(VI) and Cr(III) in coal combustion by-products, principally fly-ash and bottom ash. The method, which is based on the relative heights of the pre-edge peaks for the different Cr oxidati...

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Bibliographic Details
Published in:Fuel (Guildford) 1999, Vol.78 (2), p.233-242
Main Authors: Huggins, Frank E, Najih, Mohammad, Huffman, Gerald P
Format: Article
Language:English
Subjects:
01 COAL, LIGNITE, AND PEAT
ABSORPTION
Applied sciences
BY-PRODUCTS
CHROMIUM
Chromium speciation
COAL
Coal combustion by-products
COMBUSTION
Combustion of solid fuels
Combustion. Flame
Energy
Energy. Thermal use of fuels
Exact sciences and technology
FINE STRUCTURE
NATIONAL SYNCHROTRON LIGHT SOURCE
NSLS
SPECTROSCOPY
Theoretical studies. Data and constants. Metering
XAFS spectroscopy
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Summary:Chromium X-ray absorption fine-structure (XAFS) spectroscopy has been used to determine the relative amounts of Cr(VI) and Cr(III) in coal combustion by-products, principally fly-ash and bottom ash. The method, which is based on the relative heights of the pre-edge peaks for the different Cr oxidation states in X-ray absorption near-edge structure (XANES) spectra, can be used to speciate as little as 50 ppm of chromium in ash. The results indicate that the fraction of Cr(VI) oxidation state present in combustion ash samples from most commercial combustion plants is typically below or close to the detection limit (approximately 3–5% of the total chromium). There are exceptions, however, that have been found to reach as high as 20%. Such findings provide justification for a reappraisal of whether or not chromium should be considered a significant hazardous air pollutant in coal combustion.
ISSN:0016-2361
1873-7153
DOI:10.1016/S0016-2361(98)00142-2