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Mandaliev P, Dähn R, Tits J, et al. EXAFS study of Nd(III) uptake by amorphous calcium silicate hydrates (C-S-H). J Colloid Interface Sci. 2009;342(1):1-7doi: 10.1016/j.jcis.2009.06.011.
Mandaliev, P., Dähn, R., Tits, J., Wehrli, B., & Wieland, E. (2010). EXAFS study of Nd(III) uptake by amorphous calcium silicate hydrates (C-S-H). Journal of colloid and interface science, 342(1), 1-7. https://doi.org/10.1016/j.jcis.2009.06.011
Mandaliev, P, et al. "EXAFS study of Nd(III) uptake by amorphous calcium silicate hydrates (C-S-H)." Journal of colloid and interface science vol. 342,1 (2010): 1-7. doi: https://doi.org/10.1016/j.jcis.2009.06.011
Mandaliev P, Dähn R, Tits J, Wehrli B, Wieland E. EXAFS study of Nd(III) uptake by amorphous calcium silicate hydrates (C-S-H). J Colloid Interface Sci. 2010 Feb 01;342(1):1-7. doi: 10.1016/j.jcis.2009.06.011. Epub 2009 Jun 07. PMID: 19932488.
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J Colloid Interface Sci. 2010 Feb 01;342(1):1-7. doi: 10.1016/j.jcis.2009.06.011. Epub 2009 Jun 07.

EXAFS study of Nd(III) uptake by amorphous calcium silicate hydrates (C-S-H).

Journal of colloid and interface science

P Mandaliev, R Dähn, J Tits, B Wehrli, E Wieland

Affiliations

  1. Laboratory for Waste Management, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland. [email protected]

PMID: 19932488 DOI: 10.1016/j.jcis.2009.06.011

Abstract

Calcium silicate hydrate (C-S-H) phases control the immobilization of many metal cations in cementitious materials. In this study Nd binding to amorphous C-S-H phases with different Ca/Si (C/S) mol ratios (0.56, 0.87 and 1.54) and Nd loadings (7 and 35mumol/g), and which had been aged up to 270 days, has been investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy. The structural parameters derived from EXAFS were compared with those predicted from bond-valence calculations. The study reveals that Nd may form several species in contact with C-S-H phases. The EXAFS parameters determined in samples after one day of reaction indicate the formation of inner-sphere surface complexes. The Nd-Ca and Nd-Si bond-distances tend to increase with time at both Nd loadings. Changes in the coordination numbers N(Si) and N(Ca) were found to be dependent on the (C/S) ratio. At the lowest C/S ratio the number of neighboring Si atoms tends to increase with time while the number of neighboring Ca atoms tends to increase with time at highest C/S ratio. No clear trend was observed for the medium C/S ratio. Nd incorporation into the structures of C-S-H phases is assumed to be the dominant immobilization process based on comparison with bond-distances predicted from structural considerations. After prolonged reaction times (45 days) Nd is expected to be predominantly incorporated into the Ca sheets of the C-S-H structure while small portions of Nd might also be taken up by the interlayer. The study suggests that, in the long term, amorphous C-S-H phases are capable of taking up Nd via exchange processes with Ca(2+) in the Ca sheets and the interlayer.

Copyright 2009. Published by Elsevier Inc.

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