Buffering of pH conditions in sodium bentonite

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    A bentonite buffer is a part of the engineering barrier system of the geological disposal concept for spent nuclear fuel in Finland. The chemical conditions in the bentonite porewater determine the solubility, speciation and diffusion/sorption behaviour of the radionuclides in the bentonite. The OH-groups on the edge sites of the montmorillonite, the main component of bentonite, can buffer the pH conditions especially in the case that the buffering capacity of the accessory minerals is small. In this work, the pH conditions created by the interaction of sodium montmorillonite and an acetate buffer solution were studied experimentally in batch experiments and in compacted sodium montmorillonite. In the experiment with the compacted sample, the ends of an 18.4 mm long cylinder were exposed to an external solution of 0.3 M NaCl and 0.1 M acetate adjusted to pH 5 with NaOH. The effects were monitored by measuring the pH in the montmorillonite sample at 5 mm and 9.2 mm from the solution-montmorillonite interface as a function of time. The batch experiment was modelled considering the surface reactions of montmorillonite and the dissolution reactions of calcite and the added constituents to explain the observed phenomena.
    Original languageEnglish
    Title of host publicationMRS Proceedings
    Subtitle of host publicationSymposium NW – Scientific Basis for Nuclear Waste Management XXXV
    PublisherMaterials Research Society
    ISBN (Print)978-1-6274-8264-6
    Publication statusPublished - 2012
    MoE publication typeA4 Article in a conference publication
    Event2012 MRS Spring Meeting - San Francisco, CA, United States
    Duration: 9 Apr 201213 Apr 2012

    Publication series

    SeriesMaterials Research Society Symposia Proceedings


    Conference2012 MRS Spring Meeting
    Country/TerritoryUnited States
    CitySan Francisco, CA


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