Speciation of cadmium in cement - Part I. Cd<sup>2+</sup> uptake by C-S-H: Fid-Bau Portal

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Speciation of cadmium in cement - Part I. Cd²⁺ uptake by C-S-H

Pomies, M.P. / Lequeux, N. / Boch, P.

Hazardous cadmium can be trapped in C-S-H, the main 'phase' in Portland cement. Two kinds of Cd-containing calcium silicates were synthesized: Cd/Ca silicate hydrates prepared by coprecipitation and Cd-exchanged C-S-H. In Cd-exchanged C-S-H, chemical and structural studies (ICP-AES, XRD, extended X-ray absorption fine structure (EXAFS), and nuclear magnetic resonance (NMR)) show that up to 30 wt.% Cd uptake is possible, with little structural change. XRD patterns and ²⁹Si magic angle spinning (MAS) NMR spectra are similar in Cd-free and Cd-containing C-S-H. Cd-EXAFS shows that the majority of Cd²⁺ atoms are homogeneously distributed within the C-S-H structure, although ¹¹³Cd cross-polarization (CP) MAS NMR cannot discriminate between Cd atoms in main layer location and Cd atoms in interlayer location. In Cd/Ca silicate coprecipitates, the structure is nearly amorphous and the silicate species do not polymerize to a C-S-H-like structure.

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Speciation of cadmium in cement - Part I. Cd²⁺ uptake by C-S-H

Pomies, M.P. / Lequeux, N. / Boch, P.

Hazardous cadmium can be trapped in C-S-H, the main 'phase' in Portland cement. Two kinds of Cd-containing calcium silicates were synthesized: Cd/Ca silicate hydrates prepared by coprecipitation and Cd-exchanged C-S-H. In Cd-exchanged C-S-H, chemical and structural studies (ICP-AES, XRD, extended X-ray absorption fine structure (EXAFS), and nuclear magnetic resonance (NMR)) show that up to 30 wt.% Cd uptake is possible, with little structural change. XRD patterns and ²⁹Si magic angle spinning (MAS) NMR spectra are similar in Cd-free and Cd-containing C-S-H. Cd-EXAFS shows that the majority of Cd²⁺ atoms are homogeneously distributed within the C-S-H structure, although ¹¹³Cd cross-polarization (CP) MAS NMR cannot discriminate between Cd atoms in main layer location and Cd atoms in interlayer location. In Cd/Ca silicate coprecipitates, the structure is nearly amorphous and the silicate species do not polymerize to a C-S-H-like structure.

Speciation of cadmium in cement - Part I. Cd²⁺ uptake by C-S-H

Pomies, M.P. / Lequeux, N. / Boch, P.

Hazardous cadmium can be trapped in C-S-H, the main 'phase' in Portland cement. Two kinds of Cd-containing calcium silicates were synthesized: Cd/Ca silicate hydrates prepared by coprecipitation and Cd-exchanged C-S-H. In Cd-exchanged C-S-H, chemical and structural studies (ICP-AES, XRD, extended X-ray absorption fine structure (EXAFS), and nuclear magnetic resonance (NMR)) show that up to 30 wt.% Cd uptake is possible, with little structural change. XRD patterns and ²⁹Si magic angle spinning (MAS) NMR spectra are similar in Cd-free and Cd-containing C-S-H. Cd-EXAFS shows that the majority of Cd²⁺ atoms are homogeneously distributed within the C-S-H structure, although ¹¹³Cd cross-polarization (CP) MAS NMR cannot discriminate between Cd atoms in main layer location and Cd atoms in interlayer location. In Cd/Ca silicate coprecipitates, the structure is nearly amorphous and the silicate species do not polymerize to a C-S-H-like structure.

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Title:

Speciation of cadmium in cement - Part I. Cd²⁺ uptake by C-S-H

Contributors:

Pomies, M.P. (author) / Lequeux, N. (author) / Boch, P. (author)

Published in:

Cement and Concrete Research ; 31 ; 563-569

Publication date:

2001

Size:

7 Seiten, 28 Quellen

ISSN:

DOI:

https://doi.org/10.1016/S0008-8846(00)00480-4

Type of media:

Article (Journal)

Type of material:

Print

Language:

English

Keywords:

Cadmiumion , Adsorption , chemische Synthese , chemische Fällung , Röntgenbeugung , Röntgenanalyse , Kernresonanzspektrometrie , Auger-Elektronenspektrometrie , Industrieabfall , Abfallbeseitigen , Abfallwirtschaft , Hydratation , Calciumsilicathydrat

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