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Bentonite Interaction with Saline High-pH Solutions

Published online by Cambridge University Press:  27 March 2012

Heikola Tiina  and
Vuorinen Ulla
Heikola Tiina
Affiliation:
VTT Technical Research Centre of Finland, Nuclear Energy, Otakaari 3K Espoo, P.O. Box 1000, FI-02044 VTT, FINLAND
Vuorinen Ulla
Affiliation:
VTT Technical Research Centre of Finland, Nuclear Energy, Otakaari 3K Espoo, P.O. Box 1000, FI-02044 VTT, FINLAND
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Abstract

Degradation of cementitious materials produces leachates of high pH. Such an alkaline plume, if reaching the bentonite buffer, is likely to induce mineralogical and chemical changes in bentonite over long times and may jeopardise the set safety function of the buffer.The objective of this ongoing research is to study the possible alterations of two bentonites, MX-80 and Deponit CA-N, in alkaline leachates at two different temperatures. Also the buffering capacity of the bentonites against high pH will be evaluated.

The ongoing batch experiments are carried out in an anaerobic glove-box (Ar atmosphere, low CO2) at two temperatures (25/60 °C) with three types of simulated cement waters (pH 9.7/9,3, 11.3/10.2 and 12.0/10.9) at 25/0 °C) and one saline groundwater simulate (pH 8.3/7.9) as reference. The solid to liquid ratio used is 1/10. For each set of experiments there are three parallels so that bentonite alteration can be analysed after three different time periods. In the experiment each bentonite sample is leached with several batches of leaching solution. For each renewal of the leaching solution the phases are separated by centrifugation, the reacted solution withdrawn and the chemical composition analysed.

The high-pH experiments (11.3 and 12.0, at 25°C) have continuously shown an initial decrease in the pH-values after each leachate renewal, albeit less dramatic than in the beginning, indicating remaining buffering capacity of the bentonites. The other two experiments (pH 8.3 and 9.7 at 25°C) have shown rather unaltered pH-values. In general, slightly lower pH-values were observed in the Deponit CA-N samples than in those of MX-80. The main cations (Na and Ca) analysed in the leachates have shown a rather expected trends as a result of ion-exchange occurring in the bentonites. The analysed Si concentrations indicate possible dissolution of smectite. More conclusions are possible after the bentonites have been characterized. One experimental set of the 25 °C experiments has been finished and the bentonite phases are being characterized. Other experiment sets are still continued.

Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1475: Symposium NW – Scientific Basis for Nuclear Waste Management XXXV , 2012 , imrc11-1475-nw35-p33
Copyright
Copyright © Materials Research Society 2012

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References

REFERENCES

1. Fernández, R., Cuevas, J., Sánchez, L., Vigil de la Villa, R. and Leguey, S.. Applied Geochemistry 21, 977 (2006).10.1016/j.apgeochem.2006.02.016Google Scholar
2. Yamaguchi, T., Sakamoto, Y., Akai, M., Takazawa, M., Iida, Y., Tanaka, T. and Nakayama, S.. Physics and Chemistry of the Earth 32, 298 (2007).10.1016/j.pce.2005.10.003Google Scholar
3. Rozalén, M. L., Huertas, F. J., Brady, P. V., Cama, J., García-Palma, S. and Linares, J.. Geochimica et CosmochimicaActa 72, 4224 (2008).10.1016/j.gca.2008.05.065Google Scholar
4. Gates, W. P. and Bouazza, A.. Geotextiles and Geomembraes, 28, 219 (2010).10.1016/j.geotexmem.2009.10.010Google Scholar
5. Honty, M., De Craen, M., Wang, L., Czímerová, A., Pentrák, M., Stríček, I. and Van Geet, M.. Applied Geochemistry, 25, 825 (2010).10.1016/j.apgeochem.2010.03.002Google Scholar
6. CauDitCoumes, C., Courtois, S., Nectoux, D., Leclercq, S. and Bourbon, X.. Cement and Concrete Research 36, 2152 (2006).10.1016/j.cemconres.2006.10.005Google Scholar
7. Codina, M., CauDitCoumes, C., Le Bescop, P., Verdier, J. and Olliver, J.P.. Cement and Concrete Research 38, 437 (2008).10.1016/j.cemconres.2007.12.002Google Scholar
8. Kronlöf, A.. Posiva Working Report 2004-45 PosivaOy, Olkiluoto, Finland.Google Scholar
9. Savage, D., Walker, C., Arthur, R., Rochelle, C., Oda, C. and Takase, H. PhysChem Earth 32, 287 (2007).10.1016/j.pce.2005.08.048Google Scholar
10. Vuorinen, U., Lehikoinen, J., Harutake, I., Yamamoto, T. and Cruz Alonso, M.. Posiva Working Report 2004-46. PosivaOy, Olkiluoto, Finland.Google Scholar
11. Heikola, T.. Posiva Working Report 2008-92. PosivaOy, Olkiluoto, Finland.Google Scholar
12. Wolery, T. J.. EQ3 a computer program for geochemical aqueous speciation-solubility calculations: User’s guide and documentation. Lawrence Livermore National Laboratory UCRL-53414, Livermore, CA, USA. (1983).Google Scholar
13. Kumpulainen, S. and Kiviranta, L.. Posiva Working Report 2011-XX. To be published.Google Scholar
14. Kaufhold, S. and Dohrmann, R. Applied Clay Science 51, 300 (2011).10.1016/j.clay.2010.12.004Google Scholar