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Article

Geochemical, Geotechnical, and Microbiological Changes in Mg/Ca Bentonite after Thermal Loading at 150 °C

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Fuel Cycle Chemistry Department, ÚJV Řež, a. s., Hlavní 130, 250 68 Husinec, Czech Republic
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Department of Water Landscape Conservation, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Praha 6, Czech Republic
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Centre of Instrumental Techniques, Institute of Inorganic Chemistry of the Czech Academy of Sciences, Husinec-Řež 1001, 250 68 Husinec, Czech Republic
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Department of Chemistry, Faculty of Science, University of Ostrava, 30. dubna 22, 701 03 Ostrava, Czech Republic
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Department Material and Mechanical Properties, Centrum výzkumu Řež s.r.o., Hlavní 130, 250 68 Husinec, Czech Republic
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Institute for Nanomaterials, Advanced Technologies and Innovation, Technical University of Liberec, Bendlova 7, 460 01 Liberec, Czech Republic
*
Author to whom correspondence should be addressed.
Academic Editors: Ana María Fernández, Stephan Kaufhold, Markus Olin, Lian-Ge Zheng, Paul Wersin and James Wilson
Minerals 2021, 11(9), 965; https://doi.org/10.3390/min11090965
Received: 30 July 2021 / Revised: 27 August 2021 / Accepted: 31 August 2021 / Published: 3 September 2021
Bentonite buffers at temperatures beyond 100 °C could reduce the amount of high-level radioactive waste in a deep geological repository. However, it is necessary to demonstrate that the buffer surrounding the canisters withstands such elevated temperatures, while maintaining its safety functions (regarding long-term performance). For this reason, an experiment with thermal loading of bentonite powder at 150 °C was arranged. The paper presents changes that the Czech Mg/Ca bentonite underwent during heating for one year. These changes were examined by X-ray diffraction (XRD), thermal analysis with evolved gas analysis (TA-EGA), aqueous leachates, Cs sorption, cation exchange capacity (CEC), specific surface area (SSA), free swelling, saturated hydraulic conductivity, water retention curves (WRC), quantitative polymerase chain reaction (qPCR), and next-generation sequencing (NGS). It was concluded that montmorillonite was partially altered, in terms of the magnitude of the surface charge density of montmorillonite particles, based on the measurement interpretations of CEC, SSA, and Cs sorption. Montmorillonite alteration towards low- or non-swelling clay structures corresponded well to significantly lower swelling ability and water uptake ability, and higher saturated hydraulic conductivity of thermally loaded samples. Microbial survivability decreased with the thermal loading time, but it was not completely diminished, even in samples heated for one year. View Full-Text
Keywords: magnesium bentonite; radioactive waste disposal; thermal loading; montmorillonite content; thermal analysis with evolved gas analysis; cation exchange capacity; specific surface area; saturated hydraulic conductivity; water retention curves; microbial survivability magnesium bentonite; radioactive waste disposal; thermal loading; montmorillonite content; thermal analysis with evolved gas analysis; cation exchange capacity; specific surface area; saturated hydraulic conductivity; water retention curves; microbial survivability
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MDPI and ACS Style

Kašpar, V.; Šachlová, Š.; Hofmanová, E.; Komárková, B.; Havlová, V.; Aparicio, C.; Černá, K.; Bartak, D.; Hlaváčková, V. Geochemical, Geotechnical, and Microbiological Changes in Mg/Ca Bentonite after Thermal Loading at 150 °C. Minerals 2021, 11, 965. https://doi.org/10.3390/min11090965

AMA Style

Kašpar V, Šachlová Š, Hofmanová E, Komárková B, Havlová V, Aparicio C, Černá K, Bartak D, Hlaváčková V. Geochemical, Geotechnical, and Microbiological Changes in Mg/Ca Bentonite after Thermal Loading at 150 °C. Minerals. 2021; 11(9):965. https://doi.org/10.3390/min11090965

Chicago/Turabian Style

Kašpar, Vlastislav, Šárka Šachlová, Eva Hofmanová, Bára Komárková, Václava Havlová, Claudia Aparicio, Kateřina Černá, Deepa Bartak, and Veronika Hlaváčková. 2021. "Geochemical, Geotechnical, and Microbiological Changes in Mg/Ca Bentonite after Thermal Loading at 150 °C" Minerals 11, no. 9: 965. https://doi.org/10.3390/min11090965

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