SREL Reprint #2556

 

 

 

X-ray absorption spectroscopy study of immobilization processes for heavy metals in calcium silicate hydrates. 2. Zinc

Jérôme Rose1, Isabelle Moulin1, Armand Masion1, Paul M. Bertsch2, Mark R. Weisner3,
Jean-Yves Bottero1, Franqis Mosnier4, and Claude Haehnel5

1CEREGE Equipe physico-chimie des interfaces, UMR 6635, CNRS/Université Aix-Marseille III,
Europole Méditerranéen de l'Arbois, BP80, 13545 Aix en Provence Cedex 4, France
2SREL, University of Georgia, PO Drawer E, Aiken, South Carolina 29802
3Department of Environmental Science and Engineering, Rice University, 6100 Main Street,
Houston, Texas 77005-1892
4CIRSEE, 38 Avenue du Président Wilson, 78230 Le Pecq, France
5ATILH La Défense 4, 7 place de la Défense, 92974 Paris la Défense Cedex, France

Abstract: Tricalcium silicate (C3S), the major phase of cement-based materials, contains naturally a few hundred parts per million of heavy metals. An X-ray absorption spectroscopy (XAS) study at the Zn K-edge has been carried out to elucidate the binding mechanisms of Zn by calcium silicate hydrates, which is important to predict the long-term behavior of Zn. At low concentration, under the threshold of precipitation of the oxide, oxy hydroxide, and calcium zinc hydroxide, no retardation of the hydration of the C3S has been observed for C3S doped with Zn. A previous 29Si NMR (Moulin, I.; Stone, W. E. E.; Sanz, J.; Bottero, J.-Y.; Mosnier, J-Y.; Haehnel, C. Langmuir 1999, 15, 2829-2835) study has demonstrated that the structure of the hydrated C3S (called C-S-H for calcium silicate hydrates) does not change if Zn is present initially or not. XAS experiments have shown that Zn tetrahedra are incorporated within the matrix of C-S-H and linked directly at the end of the silicate chains through Zn-O-Si bonds. The Zn-Si distance is ≈3.1Å. Extended X-ray absorption fine structure results have been confirmed by ab initio calculations including multiple scattering.

SREL Reprint #2556

Rose, J., I. Moulin, A. Masion, P. M. Bertsch, M. R. Wiesner, J. Y. Bottero, F. Mosnier, and C. Haehnel. 2001. X-ray absorption spectroscopy study of immobilization processes for heavy metals in calcium silicate hydrates. 2. Zinc. Langmuir 17:3658-3665.

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