Analysis of barium retention mechanisms on calcium silicate hydrate phases

Calcium silicate hydrate (C-S-H) phases mostly contribute to contaminant retention in cement. The adsorption mechanisms of Ba on C-S-H phases with four different Ca/Si ratios were investigated by batch sorption experiments. The sorption kinetics, the effects of the solid to liquid ratio and the pres...

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Bibliographic Details
Published in:Cement and concrete research 2017-03, Vol.93, p.8-16
Main Authors: Missana, Tiziana, García-Gutiérrez, Miguel, Mingarro, Manuel, Alonso, Ursula
Format: Article
Language:English
Subjects:
Adsorption
Alkalies
Alkalis
Calcium silicate hydrate
Calcium silicate hydrate (C-S-H) gels
Calcium silicates
Cements
Contaminants
Earth alkaline metals
Isotherms
Phases
Radioactive waste
Reaction kinetics
Silicon
Sorption
Surface chemistry
Thermodynamic modelling
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Summary:Calcium silicate hydrate (C-S-H) phases mostly contribute to contaminant retention in cement. The adsorption mechanisms of Ba on C-S-H phases with four different Ca/Si ratios were investigated by batch sorption experiments. The sorption kinetics, the effects of the solid to liquid ratio and the presence of alkalis in solution were analysed. Sorption isotherms in a wide range of Ba concentrations (from 10−10 to 1·10−1M) were performed. To understand the underlying retention mechanisms, the effects of Ba adsorption on surface potentials were additionally examined. The main objective of this study was to develop a sorption model able reproducing not only the Ba sorption behaviour, but also the C-S-H surface potential before and after Ba uptake. The reactions and model parameters selected for satisfying these conditions are discussed in the paper. A three-site model, with weak and strong silanol sites and one exchange site, which satisfactorily fulfils the initial aims, is proposed. [Display omitted]
ISSN:0008-8846
1873-3948
DOI:10.1016/j.cemconres.2016.12.004