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CO2 effect on the pH of compacted bentonite buffer on the laboratory scale

Published online by Cambridge University Press:  09 July 2018

A. Itäla ,
J. Järvinen  and
A. Muurinen
A. Itäla
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
J. Järvinen
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
A. Muurinen
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
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Abstract

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Disposal of Finnish spent nuclear fuel is planned to be based on the KBS-3 repository concept. The role of the bentonite buffer in this concept is essential, and thus the behaviour of the bentonite has to be known. The experiments in this paper concentrated on providing information about the effects of carbon dioxide CO2(g) partial pressure on compacted sodium bentonite, giving an insight into the buffering capacity. The experimental setup consisted of a hermetic box which had a CO2-adjusted atmosphere, and the bentonite was in contact with this atmosphere through water reservoirs. The results indicated that it is possible to measure online the changing pH in the porewater inside compacted bentonite using IrOx electrodes. It was found that the pH fell if the CO2 partial pressure increased above atmospheric conditions. The experimental results indicated a greater fall in pH than in our model in the test cases where CO2 was present. The pH in the experiment with 0 PCO2 remained nearly constant throughout the 5 month period. On the other hand, the pH dropped to near 6 with 0.3 PCO2 and to 5.5 with 1 PCO2.

Keywords

bentonitepHcarbon dioxidebufferalterationcompaction
Type
Research Article
Information
Clay Minerals , Volume 48 , Issue 2 , May 2013 , pp. 277 - 284
Creative Commons
Creative Common License - CCCreative Common License - BY
Copyright © The Mineralogical Society of Great Britain and Ireland 2013 This is an Open Access article, distributed under the terms of the Creative Commons Attribution license. (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

References

Blanc, P., Lassin, A. & Piantone, P. (2007) Thermoddem: a Database Devoted to Waste Minerals. BRGM (Orléans, France). http://thermoddem.brgm.fr Google Scholar
Bourg, I.C., Sposito, G. & Bourg, A.C.M. (2007) Modeling the acid-base surface chemistry of montmorillonite. Journal of Colloid and Interface Science, 312, 297–310., doi : 10.1016/j.jcis.2007.03.062.Google Scholar
Bradbury, M.H. & Baeyens, B. (1997) A mechanistic description of Ni and Zn sorption on Na-montmorillonite. Journal of Contaminant Hydrology, 27, 223–248. doi: 10.1016/S0169-7722(97)00007-7.Google Scholar
Bradbury, M.H. & Baeyens, B. (1998) A physicochemical characterisation and geochemical modelling approach for determining porewater chemistries in argillaceous rocks. Goechimica et Cosmochimica Acta, 62, 783–795. doi : 10.1016/S0016- 7037(97)00387-6.Google Scholar
Bradbury, M.H. & Baeyens, B. (2002) Porewater Chemistry in Compacted Re-saturated MX-80 Bentonite: Physico-Chemical Characterisation and Geochemical Modelling. PSI Bericht Nr. 02-10, Villigen, 42 pp.Google Scholar
Grauer, R. (1986) Bentonite as a Backfill Material in the High Level Waste Repository: Chemical Aspects. Nagra Technical Report NTB 86-12E, Villigen, 130 pp.Google Scholar
Kaufhold, S. & Dohrmann, R. (2013) The variable charge of dioctahedral clay minerals. Journal of Colloid and Interface Science, 390, 225–233.10.1016/j.jcis.2012.09.023CrossRefGoogle Scholar
Kaufhold, S., Dohrmann, R., Koch, D. & Houben, G. (2008) The pH of aqueous bentonite suspensions. Clays and Clay Minerals, 56, 338–343.10.1346/CCMN.2008.0560304Google Scholar
Kiviranta, L. & Kumpulainen, S. (2011) Quality Control and Characterization of Bentonite Materials. Posiva Oy, Olkiluoto, Finland, Working Report 2011-84.Google Scholar
Kohličková, M. & Jedináková-Křižová, V. (1998) Effect of pH and Eh on the sorption of selected radionuclides. Journal of Radioanalytical and Nuclear Chemistry, 229, 43–48. doi: 10.1007/BF02389444.Google Scholar
Kumpulainen, S. & Kiviranta, L. (2010) Mineralogical and chemical characterization of various bentonite and smectite-rich clay materials. Part A. Comparison and development of mineralogical characterization methods Part B: Mineralogical and chemical characterization of clay materials. Posiva Oy, Olkiluoto, Finland, Working Report 2010-52, 74 pp.Google Scholar
Muurinen, A. & Carlsson, T. (2007) Development of methods for on-line measurements of chemical conditions in compacted bentonite. Physics and Chemistry of Earth, 32, 241–246. doi: 10.1016/j.pce.2006.02.059.CrossRefGoogle Scholar
Muurinen, A. & Carlsson, T. (2010) Experiences of pH and Eh measurements in compacted MX-80 bentonite. Applied Clay Science, 40, 23–27. doi: 10.1016/j.clay.2008.05.007.Google Scholar
Muurinen, A. & Lehikoinen, J. (1999) Porewater Chemistry in Compacted Bentonite. Posiva Report.Google Scholar
Pastina, B. & Hellä, P. (2006) Expected Evolution of a Spent Nuclear Fuel Repository at Olkiluoto. Posiva Oy, Olkiluoto, Finland, Posiva Report 2006-05, 405 pp.Google Scholar
Wersin, P. (2003) Geochemical modelling of bentonite porewater in high-level waste repositories. Journal of Contaminant Hydrology, 61, 405–422.10.1016/S0169-7722(02)00119-5Google Scholar