Development of methods for on-line measurements of chemical conditions in compacted bentonite

Arto Muurinen (Corresponding Author), Torbjörn Carlsson

    Research output: Contribution to journalArticleScientificpeer-review

    8 Citations (Scopus)

    Abstract

    This work describes the development of an on-line method for studying the chemical conditions in compacted water-saturated bentonite.
    The equipment includes a squeezing cell, measurement electrodes, a reference electrode, and a data-logging system. IrOx wire was used for the pH measurements and Au and Pt wires for the redox measurements.
    The electrodes were made in-house at VTT. The reference electrode was a commercial leak-free electrode. The measurement electrodes were installed in the bentonite, while the reference electrode was placed in water outside the clay.
    The contact between the reference electrode and the measurement electrodes was established via the solution in a tube.

    The work included first a test and calibration of the electrodes in various standard solutions. The performance of the electrodes was subsequently studied in compacted MX-80 in squeezing cell experiments.
    The squeezing cell initially contained MX-80 mixed with different solutions at a dry density of 0.8–0.9 Mg/m3. The pore water was then slowly squeezed out from the clay until the final density of 1.5 Mg/m3 was reached.
    The measurement electrodes were then placed in the clay and the potential measurements were started. At the end of the experiments the electrodes were removed from bentonite and recalibrated.
    The pH and Eh in the squeezed pore waters were determined for comparison.

    The results obtained so far have led to the conclusion that it is possible to perform pH measurements in compacted bentonite by using IrOx electrodes.
    The electrode can survive the swelling pressure inside compacted water-saturated clay without losing its ability to function as a pH electrode.
    It is also possible to perform Eh measurements in compacted clay by using Au and Pt electrodes.

    Original languageEnglish
    Pages (from-to)241-246
    JournalPhysics and Chemistry of the Earth
    Volume32
    Issue number1-7
    DOIs
    Publication statusPublished - 2007
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Bentonite
    bentonite
    electrode
    Electrodes
    electrodes
    clays
    clay
    compressing
    Water
    chemical
    method
    water
    porewater
    cells
    wire
    Wire
    porosity
    dry density

    Keywords

    • pH
    • Eh
    • bentonite
    • iridium electrode
    • gold electrode
    • platinum electrode
    • nuclear waste
    • nuclear waste management
    • radionuclide migration
    • radionuclides

    Cite this

    Muurinen, Arto ; Carlsson, Torbjörn. / Development of methods for on-line measurements of chemical conditions in compacted bentonite. In: Physics and Chemistry of the Earth. 2007 ; Vol. 32, No. 1-7. pp. 241-246.
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    Development of methods for on-line measurements of chemical conditions in compacted bentonite. / Muurinen, Arto (Corresponding Author); Carlsson, Torbjörn.

    In: Physics and Chemistry of the Earth, Vol. 32, No. 1-7, 2007, p. 241-246.

    Research output: Contribution to journalArticleScientificpeer-review

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    AU - Muurinen, Arto

    AU - Carlsson, Torbjörn

    PY - 2007

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    N2 - This work describes the development of an on-line method for studying the chemical conditions in compacted water-saturated bentonite. The equipment includes a squeezing cell, measurement electrodes, a reference electrode, and a data-logging system. IrOx wire was used for the pH measurements and Au and Pt wires for the redox measurements. The electrodes were made in-house at VTT. The reference electrode was a commercial leak-free electrode. The measurement electrodes were installed in the bentonite, while the reference electrode was placed in water outside the clay. The contact between the reference electrode and the measurement electrodes was established via the solution in a tube.The work included first a test and calibration of the electrodes in various standard solutions. The performance of the electrodes was subsequently studied in compacted MX-80 in squeezing cell experiments. The squeezing cell initially contained MX-80 mixed with different solutions at a dry density of 0.8–0.9 Mg/m3. The pore water was then slowly squeezed out from the clay until the final density of 1.5 Mg/m3 was reached. The measurement electrodes were then placed in the clay and the potential measurements were started. At the end of the experiments the electrodes were removed from bentonite and recalibrated. The pH and Eh in the squeezed pore waters were determined for comparison.The results obtained so far have led to the conclusion that it is possible to perform pH measurements in compacted bentonite by using IrOx electrodes.The electrode can survive the swelling pressure inside compacted water-saturated clay without losing its ability to function as a pH electrode. It is also possible to perform Eh measurements in compacted clay by using Au and Pt electrodes.

    AB - This work describes the development of an on-line method for studying the chemical conditions in compacted water-saturated bentonite. The equipment includes a squeezing cell, measurement electrodes, a reference electrode, and a data-logging system. IrOx wire was used for the pH measurements and Au and Pt wires for the redox measurements. The electrodes were made in-house at VTT. The reference electrode was a commercial leak-free electrode. The measurement electrodes were installed in the bentonite, while the reference electrode was placed in water outside the clay. The contact between the reference electrode and the measurement electrodes was established via the solution in a tube.The work included first a test and calibration of the electrodes in various standard solutions. The performance of the electrodes was subsequently studied in compacted MX-80 in squeezing cell experiments. The squeezing cell initially contained MX-80 mixed with different solutions at a dry density of 0.8–0.9 Mg/m3. The pore water was then slowly squeezed out from the clay until the final density of 1.5 Mg/m3 was reached. The measurement electrodes were then placed in the clay and the potential measurements were started. At the end of the experiments the electrodes were removed from bentonite and recalibrated. The pH and Eh in the squeezed pore waters were determined for comparison.The results obtained so far have led to the conclusion that it is possible to perform pH measurements in compacted bentonite by using IrOx electrodes.The electrode can survive the swelling pressure inside compacted water-saturated clay without losing its ability to function as a pH electrode. It is also possible to perform Eh measurements in compacted clay by using Au and Pt electrodes.

    KW - pH

    KW - Eh

    KW - bentonite

    KW - iridium electrode

    KW - gold electrode

    KW - platinum electrode

    KW - nuclear waste

    KW - nuclear waste management

    KW - radionuclide migration

    KW - radionuclides

    U2 - 10.1016/j.pce.2006.02.059

    DO - 10.1016/j.pce.2006.02.059

    M3 - Article

    VL - 32

    SP - 241

    EP - 246

    JO - Physics and Chemistry of the Earth

    JF - Physics and Chemistry of the Earth

    SN - 1474-7065

    IS - 1-7

    ER -