XAFS study of the chemical and structural states of technetium in Fe(III) oxide Co-precipitates

Steve M. Heald, John M. Zachara, Byong Hun Jeon, James P. McKinley, Ravi Kukkadapu, Dean Moore

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

XAFS has been used to study the chemical state and structural environment of technetium in Fe(III) oxide co-precipitates. 99Technetium is an abundant fission product which poses a significant environmental hazard due to its long half-life, abundance in nuclear wastes, and environmental mobility as the pertechnetate ion [Tc(VII)O4-] under oxidizing conditions. Tetravalent Tc [Tc(IV)] is the stable valence state under reducing or anoxic conditions where its environmental mobility is significantly lowered by formation of a sparingly soluble, hydrated amorphous oxide precipitate [Tc(IV)O2nH2O(s)]. We have been studying the kinetics and solid products resulting from abiotic reduction of Tc(VII)O4 - by aqueous, adsorbed, and structural Fe(II) to provide insights on Tc migration in microaerophilic groundwaters. The reduction reaction yields Fe/Tc precipitates of variable structures that have not been previously studied. For the homogeneous reaction with aqueous Fe(II) at relatively high Tc:Fe concentrations, the predominant redox product is a solid containing Tc(IV) dimers attached in a bidentate edge-sharing configuration to FeO6 octahedra on the surface or unoccupied interior sites of a ferrihydrite-like precipitate. A similar ferrihydrite-type solid is formed on the surface of Fe oxide minerals such a hematite and goethite following the heterogeneous reaction of Tc(VII)O4- with surface-complexed Fe(II). These co-precipitates greatly slow the oxidation rate of Tc(IV) relative to amorphous Tc(IV)O2nH2O(s), possibly allowing for the long term sequestration of 99Tc in stable (bio)geochemical mineral forms that may reduce the long term environmental risk of 99Tc subsurface contamination.

Original languageEnglish
Title of host publicationX-RAY ABSORPTION FINE STRUCTURE - XAFS13
Subtitle of host publication13th International Conference
Pages173-175
Number of pages3
DOIs
StatePublished - 2007 Mar 26
EventX-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference - Stanford, CA, United States
Duration: 2006 Jul 92006 Jul 14

Publication series

NameAIP Conference Proceedings
Volume882
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

OtherX-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference
CountryUnited States
CityStanford, CA
Period06/07/906/07/14

Keywords

  • Iron oxides
  • Technetium
  • XAFS

Fingerprint Dive into the research topics of 'XAFS study of the chemical and structural states of technetium in Fe(III) oxide Co-precipitates'. Together they form a unique fingerprint.

  • Cite this

    Heald, S. M., Zachara, J. M., Jeon, B. H., McKinley, J. P., Kukkadapu, R., & Moore, D. (2007). XAFS study of the chemical and structural states of technetium in Fe(III) oxide Co-precipitates. In X-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference (pp. 173-175). (AIP Conference Proceedings; Vol. 882). https://doi.org/10.1063/1.2644465