Chemical speciation of uranium in contaminated and chemically remediated soils by micro X-ray absorption spectroscopy
Conference
·
OSTI ID:210170
- Univ. of Georgia, Aiken, SC (United States)
Spatially resolved XAS and X-ray fluorescence spectroscopic studies were conducted to investigate the distribution and chemical speciation of uranium (U) in contaminated soils and sediments prior to and following chemical extraction. This approach provided direct information on the chemical speciation of uranium in micro-regions of contaminated soils and sediments sampled at the Fernald Environmental Management Project Site and the Savannah River Site. Using X-ray absorption near edge structure (XANES) spectroscopy, the predominant oxidation state of uranium in the contaminated sediments was determined. A calibration method was developed which enhanced the ability to collect oxidation state information at much lower concentrations in a reasonable time frame and allowed for the generation of oxidation state distribution maps at a 20 {mu}m spatial resolution. Additional experiments conducted on mixed uranium containing mineral phases confirmed the ability of the method to accurately delineate proportions of uranium in different oxidation states. Furthermore, a method of imbedding particles in a nonreactive silicon polymer was developed such that individual particles could be examined before and after extraction with a wide range of chemicals used in sequential extraction techniques and others proposed for chemical intervention technologies. Studies revealed that the sodium carbonate treatment proposed to extract U from soils efficiently removed U(VI), except when present as a phosphate phase, and was inefficient at extracting U(IV) phases. The results of these studies demonstrated the utility of spatially resolved XAS methods for in situ chemical speciation of U and other metals and metalloids.
- OSTI ID:
- 210170
- Report Number(s):
- CONF-9509139--
- Country of Publication:
- United States
- Language:
- English
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