Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2)

Autor:	Daniel Svensson, Paul Wersin, Jean-Marc Greneche, Patrik Sellin, Andreas Jenni, Jebril Hadi, Olivier X. Leupin
Rok vydání:	2021
Předmět:	Materials science Scanning electron microscope bentonite Inorganic chemistry Geology Mineralogy Geotechnical Engineering and Engineering Geology Cementation (geology) Redox Corrosion iron in situ experiment 550 Earth sciences & geology Bentonite medicine interface Ferric Clay minerals QE351-399.2 medicine.drug Mossbauer spectrometry
Zdroj:	Wersin, Paul; Hadi, Jebril; Jenni, Andreas; Svensson, Daniel; Greneche, Jean-Marc; Sellin, Patrik; Leupin, Olivier (2021). Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2). Minerals, 11(8), p. 907. MDPI 10.3390/min11080907 Minerals Volume 11 Issue 8 Minerals, Vol 11, Iss 907, p 907 (2021)
ISSN:	2075-163X
DOI:	10.3390/min11080907
Popis:	Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by “bulk” methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found.
Databáze:	OpenAIRE
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