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Evaluation of Sorption Behavior of Iodide Ions on Calcium Silicate Hydrate and Hydrotalcite

Published online by Cambridge University Press:  08 April 2015

Taiji Chida
Affiliation:
Dept. of Quantum Science & Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 JAPAN
Jun Furuya
Affiliation:
Dept. of Quantum Science & Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 JAPAN
Yuichi Niibori
Affiliation:
Dept. of Quantum Science & Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 JAPAN
Hitoshi Mimura
Affiliation:
Dept. of Quantum Science & Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 JAPAN
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Abstract

The migration retardation of anionic radionuclides, notably I-129, in radioactive waste repositories is one of the most critical factors for improving the performance of engineered barriers. To gain more fundamental knowledge required to make such improvements, this study examined the sorption behavior of iodide ions on calcium silicate hydrate (CSH) and hydrotalcite (HT), which act as anion exchangers. CSH was synthesized using CaO and fumed silica, with Ca/Si molar ratios ranging from 0.4 to 1.6. The weight ratio of CSH to HT was 1.0. These solid samples were immersed for 14 days in a 30 mL sample of pure water or 0.6 M NaCl solution, each of which contained 0.5 mM iodide ions with a given liquid/solid weight ratio (10, 15, or 20). Raman spectroscopy studies indicated that the structures of CSH and HT were maintained during the hydration of the solid phase and the sorption of iodide ions. The distribution coefficients for the sorption of iodide ions on CSH and HT ranged from 6 to 13 L/kg for pure water and from 1 to 2 L/kg for NaCl solution. These retardation effects for iodide ions would contribute toward improving the performance of the repository system as most conventional safety assessments assume that iodide ions hardly sorb on engineered barriers such as cementitious materials.

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Articles
Copyright
Copyright © Materials Research Society 2015 

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References

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