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

Bonhoure, Isabelle / Baur, Isabel / Wieland, Erich / Johnson, C.Annette / Scheidegger, Andre M.

The uptake of selenate (Se^VIO₄^2-) or selenite (Se^IVO ₃^2-) 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 SeO₄ ^2- and SeO₃^2- 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 SeO₄^2- and SeO₃^2- entities is maintained upon immobilization by HCP and cement minerals and non-specific interactions dominate at the given Se loadings.

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

Bonhoure, Isabelle / Baur, Isabel / Wieland, Erich / Johnson, C.Annette / Scheidegger, Andre M.

The uptake of selenate (Se^VIO₄^2-) or selenite (Se^IVO ₃^2-) 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 SeO₄ ^2- and SeO₃^2- 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 SeO₄^2- and SeO₃^2- entities is maintained upon immobilization by HCP and cement minerals and non-specific interactions dominate at the given Se loadings.

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

Bonhoure, Isabelle / Baur, Isabel / Wieland, Erich / Johnson, C.Annette / Scheidegger, Andre M.

The uptake of selenate (Se^VIO₄^2-) or selenite (Se^IVO ₃^2-) 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 SeO₄ ^2- and SeO₃^2- 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 SeO₄^2- and SeO₃^2- entities is maintained upon immobilization by HCP and cement minerals and non-specific interactions dominate at the given Se loadings.

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Title:

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

Contributors:

Bonhoure, Isabelle (author) / Baur, Isabel (author) / Wieland, Erich (author) / Johnson, C.Annette (author) / Scheidegger, Andre M. (author)

Published in:

Cement and Concrete Research ; 36 ; 91-98

Publication date:

2006

Size:

8 Seiten, 35 Quellen

ISSN:

DOI:

https://doi.org/10.1016/j.cemconres.2005.05.003

Type of media:

Article (Journal)

Type of material:

Print

Language:

English

Keywords:

Selen , Anion , Aushärten , Röntgenstrahl , optische Absorption , Röntgenfluoreszenzspektrometrie , Absorptionsspektrometrie , radioaktiver Abfall , Redoxreaktion , Adsorption , Rückwärtsstreuung , Zementpaste , Erhärten (Zementabbinden) , Selenit , CSH (Calciumsilicathydrat)

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