Ion concentration caused by an external solution into the porewater of compacted bentonite

Arto Muurinen (Corresponding Author), Ola Karnland, Jarmo Lehikoinen

Research output: Contribution to journalArticleScientificpeer-review

29 Citations (Scopus)

Abstract

The concentrations caused by the external solution into the porewater were studied with compacted bentonite (MX-80), from which easily dissolving components had been removed in order to ensure that the ions in the porewater came from the external solution. The dry densities of the samples varied from 700 to 1700 kg/m3 and NaCl solutions of 0.1–3 M were used as the external solution for saturation. The concentrations in the porewater were determined by the direct analysis of the squeezed porewaters and by dispersing the sample in deionized water. At high concentrations, the Donnan model can predict the concentrations in the porewater rather well. At low concentrations, where the ion exclusion is stronger, the measured concentrations are clearly higher than the modelled values. One possible explanation for this discrepancy is the microstructure of the bentonite, and an attempt to couple the effects of the microstructure and the Donnan model was made. It was assumed that there are two pore types, interlamellar pores in the montmorillonite stacks and large pores in the gel between the stacks. The dimensions of the microstructure were obtained from SAXS and BET(N2) measurements. In this case, the fitting is much better, which supports the assumption of different pore types in bentonite.

Original languageEnglish
Pages (from-to)119-127
JournalPhysics and Chemistry of the Earth
Volume29
Issue number1
DOIs
Publication statusPublished - 2004
MoE publication typeA1 Journal article-refereed

Fingerprint

Bentonite
bentonite
ion concentration
porewater
Ions
ion
porosity
microstructure
Microstructure
Saturation (materials composition)
Deionized water
dry density
dispersing
montmorillonite
exclusion
Gels
low concentrations
dissolving
ions
gel

Keywords

  • bentonite
  • nuclear waste
  • porosity
  • exclusion
  • microstructure
  • Donnan model

Cite this

Muurinen, Arto ; Karnland, Ola ; Lehikoinen, Jarmo. / Ion concentration caused by an external solution into the porewater of compacted bentonite. In: Physics and Chemistry of the Earth. 2004 ; Vol. 29, No. 1. pp. 119-127.
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Ion concentration caused by an external solution into the porewater of compacted bentonite. / Muurinen, Arto (Corresponding Author); Karnland, Ola; Lehikoinen, Jarmo.

In: Physics and Chemistry of the Earth, Vol. 29, No. 1, 2004, p. 119-127.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Karnland, Ola

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AB - The concentrations caused by the external solution into the porewater were studied with compacted bentonite (MX-80), from which easily dissolving components had been removed in order to ensure that the ions in the porewater came from the external solution. The dry densities of the samples varied from 700 to 1700 kg/m3 and NaCl solutions of 0.1–3 M were used as the external solution for saturation. The concentrations in the porewater were determined by the direct analysis of the squeezed porewaters and by dispersing the sample in deionized water. At high concentrations, the Donnan model can predict the concentrations in the porewater rather well. At low concentrations, where the ion exclusion is stronger, the measured concentrations are clearly higher than the modelled values. One possible explanation for this discrepancy is the microstructure of the bentonite, and an attempt to couple the effects of the microstructure and the Donnan model was made. It was assumed that there are two pore types, interlamellar pores in the montmorillonite stacks and large pores in the gel between the stacks. The dimensions of the microstructure were obtained from SAXS and BET(N2) measurements. In this case, the fitting is much better, which supports the assumption of different pore types in bentonite.

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