Uptake of Se(IV/VI) oxyanions by hardened cement paste and cement minerals: An X-ray absorption spectroscopy study

Journal Article · Sun Jan 15 00:00:00 EST 2006 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2005.0· OSTI ID:20793266

Bonhoure, Isabelle ^[1]; Baur, Isabel ^[2]; Wieland, Erich ^[1]; Johnson, C Annette ^[2]; Scheidegger, Andre M ^[1]

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1. Laboratory for Waste Management, Nuclear Energy and Safety Department, Paul Scherrer Institute, 5232 Villigen (Switzerland)
2. Swiss Federal Institute for Environmental Science and Technology (EAWAG), 8600 Duebendorf (Switzerland)

The uptake of selenate (Se{sup VI}O{sub 4} {sup 2-}) or selenite (Se{sup IV}O{sub 3} {sup 2-}) by hardened cement paste (HCP) and important constituents of the cement matrix such as calcium silicate hydrate (C-S-H), portlandite (CH), ettringite (AFt) and monosulfate (AFm) was investigated using X-ray absorption spectroscopy (XAS). The XAS measurements were conducted on samples with Se loadings ranging between 1200 and 8800 ppm. X-ray absorption near edge structure (XANES) spectroscopy shows that redox reactions do not influence uptake processes in the cementitious systems. The EXAFS (extended X-ray absorption fine structure) spectra of Se(IV) and Se(VI) bound to CH, AFt, AFm and C-S-H are similar to those of SeO{sub 4} {sup 2-} and SeO{sub 3} {sup 2-} in solution, indicating a 'solution-like' coordination environment upon uptake by the cement minerals. Similarly, the spectra of Se(IV)- and Se(VI)-treated HCP samples reveal the absence of backscattering atoms at short distances. These results suggest that the coordination sphere of the SeO{sub 4} {sup 2-} and SeO{sub 3} {sup 2-} entities is maintained upon immobilization by HCP and cement minerals and non-specific interactions dominate at the given Se loadings.

• OSTI ID: 20793266
• Journal Information: Cement and Concrete Research, Vol. 36, Issue 1; Other Information: DOI: 10.1016/j.cemconres.2005.05.003; PII: S0008-8846(05)00143-2; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION
ABSORPTION SPECTROSCOPY
ATOMIC FORCE MICROSCOPY
CALCIUM SILICATES
CEMENTS
HCP LATTICES
RADIOACTIVE WASTES
SELENATES
SELENITES
X-RAY SPECTROSCOPY