Effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite

Arto Muurinen (Corresponding Author), O. Karnland, Jarmo Lehikoinen

    Research output: Contribution to journalArticleScientificpeer-review

    21 Citations (Scopus)

    Abstract

    In the present work, the effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite was studied. The experiments were performed with MX-80 bentonite, from which easily dissolving components, e.g. chlorides and gypsum, had been removed to ensure that the excess ions in the pore water came from the external solution alone. In the first case, the bentonite was homogenized by dispersing the clay powder in deionized water with ultrasound.
    The extra water was subsequently squeezed out in order to obtain the desired clay density. In the second case, the samples were compacted to the desired density at the outset and then saturated with deionized water.
    Thereafter, both sample types were equilibrated with 0.1 M NaCl solution through filter plates. In the third case, the compacted samples were equilibrated directly with 0.1 M NaCl solution. The concentrations in the pore water at the end of equilibration were determined by dispersing the bentonite samples in deionized water.
    The concentrations in the pore water of the samples saturated first with deionized water were clearly lower than those saturated directly with 0.1 M NaCl solution. This probably reflects the effect of homogenization and a smaller size of the external pores on the chloride concentrations.
    The model results calculated with the Donnan model by assuming a homogenous bentonite structure were lower than the measured values. Excellent agreement between experimental and model results could be obtained by assuming a dual-porosity structure.
    Original languageEnglish
    Pages (from-to)485-490
    JournalPhysics and Chemistry of the Earth
    Volume32
    Issue number1 - 7
    DOIs
    Publication statusPublished - 2007
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Bentonite
    bentonite
    homogenizing
    exclusion
    Deionized water
    Chlorides
    microstructure
    chlorides
    chloride
    Microstructure
    porewater
    Water
    water
    porosity
    dispersing
    Calcium Sulfate
    clay
    dual porosity
    clays
    Powders

    Keywords

    • bentonite
    • nuclear waste
    • nuclear waste management
    • porosity
    • exclusion
    • microstructure
    • Donnan model
    • radionuclide migration
    • radionuclides

    Cite this

    Muurinen, Arto ; Karnland, O. ; Lehikoinen, Jarmo. / Effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite. In: Physics and Chemistry of the Earth. 2007 ; Vol. 32, No. 1 - 7. pp. 485-490.
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    Effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite. / Muurinen, Arto (Corresponding Author); Karnland, O.; Lehikoinen, Jarmo.

    In: Physics and Chemistry of the Earth, Vol. 32, No. 1 - 7, 2007, p. 485-490.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite

    AU - Muurinen, Arto

    AU - Karnland, O.

    AU - Lehikoinen, Jarmo

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    N2 - In the present work, the effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite was studied. The experiments were performed with MX-80 bentonite, from which easily dissolving components, e.g. chlorides and gypsum, had been removed to ensure that the excess ions in the pore water came from the external solution alone. In the first case, the bentonite was homogenized by dispersing the clay powder in deionized water with ultrasound. The extra water was subsequently squeezed out in order to obtain the desired clay density. In the second case, the samples were compacted to the desired density at the outset and then saturated with deionized water. Thereafter, both sample types were equilibrated with 0.1 M NaCl solution through filter plates. In the third case, the compacted samples were equilibrated directly with 0.1 M NaCl solution. The concentrations in the pore water at the end of equilibration were determined by dispersing the bentonite samples in deionized water. The concentrations in the pore water of the samples saturated first with deionized water were clearly lower than those saturated directly with 0.1 M NaCl solution. This probably reflects the effect of homogenization and a smaller size of the external pores on the chloride concentrations. The model results calculated with the Donnan model by assuming a homogenous bentonite structure were lower than the measured values. Excellent agreement between experimental and model results could be obtained by assuming a dual-porosity structure.

    AB - In the present work, the effect of homogenization on the microstructure and exclusion of chloride in compacted bentonite was studied. The experiments were performed with MX-80 bentonite, from which easily dissolving components, e.g. chlorides and gypsum, had been removed to ensure that the excess ions in the pore water came from the external solution alone. In the first case, the bentonite was homogenized by dispersing the clay powder in deionized water with ultrasound. The extra water was subsequently squeezed out in order to obtain the desired clay density. In the second case, the samples were compacted to the desired density at the outset and then saturated with deionized water. Thereafter, both sample types were equilibrated with 0.1 M NaCl solution through filter plates. In the third case, the compacted samples were equilibrated directly with 0.1 M NaCl solution. The concentrations in the pore water at the end of equilibration were determined by dispersing the bentonite samples in deionized water. The concentrations in the pore water of the samples saturated first with deionized water were clearly lower than those saturated directly with 0.1 M NaCl solution. This probably reflects the effect of homogenization and a smaller size of the external pores on the chloride concentrations. The model results calculated with the Donnan model by assuming a homogenous bentonite structure were lower than the measured values. Excellent agreement between experimental and model results could be obtained by assuming a dual-porosity structure.

    KW - bentonite

    KW - nuclear waste

    KW - nuclear waste management

    KW - porosity

    KW - exclusion

    KW - microstructure

    KW - Donnan model

    KW - radionuclide migration

    KW - radionuclides

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    JO - Physics and Chemistry of the Earth

    JF - Physics and Chemistry of the Earth

    SN - 1474-7065

    IS - 1 - 7

    ER -