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Systematic XAS study on the reduction and uptake of Tc by magnetite and mackinawite

Yalçintaş, E.; Scheinost, A. C.; Gaona, X.; Altmaier, M.

Abstract (englisch):
The mechanisms for the reduction and uptake of Tc by magnetite (Fe3O4) and mackinawite (FeS) are investigated using X-ray absorption spectroscopy (XANES and EXAFS), in combination with thermodynamic calculations of the Tc/Fe systems and accurate characterization of the solution properties (pHm, pe, [Tc]). Batch sorption experiments were performed under strictly anoxic conditions using freshly prepared magnetite and mackinawite in 0.1 M NaCl solutions with varying initial Tc(VII) concentrations (2 × 10−5 and 2 × 10−4 M) and Tc loadings (400–900 ppm). XANES confirms the complete reduction of Tc(VII) to Tc(IV) in all investigated systems, as predicted from experimental (pHm + pe) measurements and thermodynamic calculations. Two Tc endmember species are identified by EXAFS in the magnetite system, Tc substituting for Fe in the magnetite structure and Tc–Tc dimers sorbed to the magnetite {111} faces through a triple bond. The sorption endmember is favoured at higher [Tc], whereas incorporation prevails at low [Tc] and less alkaline pH conditions. The key role of pH in the uptake mechanism is interpreted in terms of magnetite solubility, ... mehr

Zugehörige Institution(en) am KIT Institut für Nukleare Entsorgung (INE)
Publikationstyp Zeitschriftenaufsatz
Jahr 2016
Sprache Englisch
Identifikator DOI: 10.1039/c6dt02872a
ISSN: 0300-9246, 1364-5447, 1470-479X, 1472-7773, 1477-9226, 1477-9234, 1568-0258, 1570-5854
URN: urn:nbn:de:swb:90-628830
KITopen ID: 1000062883
HGF-Programm 32.01.01; LK 01
Erschienen in Dalton transactions
Band 45
Heft 44
Seiten 17874-17885
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