Mineral stability of Fe-rich bentonite in the Mock-Up-CZ experiment

Stricek, Igor; Šucha, Vladimír; Uhlík, Peter; Madejová, Jana; Galko, Igor

doi:10.2478/v10096-009-0031-2

Cited by 19 publications

(4 citation statements)

References 23 publications

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“…A detailed list of the spectral bands that correspond to the montmorillonite and other minerals present in the original and thermally treated BCV 2017 are listed in Table 3. The assignment of the bands was performed according to [38][39][40][41]. The OH deformation band at around 874 cm −1 (AlFeOH) in all the types of IR spectra of both samples indicates the significant substitution of octahedral Al +3 by Fe +3 in the montmorillonite structure.…”

Section: Infrared Spectroscopy (Ir)mentioning

confidence: 99%

Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite—The Initial State and the State following Thermal Treatment at 200 °C

et al. 2021

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Bentonites are considered to be the most suitable materials for the multibarrier system of high-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representative of Czech Ca-Mg bentonites in this respect, it has been included in the Czech Radioactive Waste Repository Authority (SÚRAO) buffer and backfill R&D programme. Detailed knowledge of processes in the material induced by thermal loading provides invaluable assistance regarding the evolution of the material under repository conditions. Samples of both original BCV 2017 bentonite and the same material thermally treated at 200 °C were characterised by means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, thermal analysis, cation exchange capacity, specific surface area (BET) measurements, the determination of the swell index, the liquid limit, the swelling pressure and water retention curves. The smectite in BCV 2017 bentonite comprises Ca-Mg montmorillonite with a significant degree of Fe3+ substitution in the octahedral sheet. Two main transformation processes were observed following heating at 200 °C over 27 months, the first of which comprised the dehydration of the montmorillonite and the subsequent reduction of the 001 basal distance from 14.5 Å (the original BCV 2017) to 9.8 Å, thus indicating the absence of water molecules in the interlayer space. The second concerned the dehydration and partial dehydroxylation of goethite. With the exception of the dehydration of the interlayer space, the PXRD and FTIR study revealed the crystallochemical stability of the montmorillonite in BCV 2017 bentonite under the selected experimental conditions. The geotechnical tests indicated no major changes in the mechanical properties of the thermally treated BCV 2017 bentonite, as demonstrated by the similar swelling pressure values. However, the variation in the swell index and the gradual increase in the liquid limit with the wetting time indicated a lower hydration rate. The retention curves consistently showed the lower retention capacity of the thermally treated samples, thus indicating the incomplete re-hydration of the thermally treated BCV 2017 exposed to air humidity and the difference in its behaviour compared to the material exposed to liquid water.

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Section: Infrared Spectroscopy (Ir)mentioning

confidence: 99%

Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite—The Initial State and the State following Thermal Treatment at 200 °C

et al. 2021

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“…This trend elucidates the origin of montmorillonite and leads to chemical weathering. An opposite development was observed in the soil profiles on bentonite deposits in temperate climates (Šucha et al 2001;Stríček et al 2006). In these cases, chemical weathering reduced T MEAN of montmorillonites primarily originating by diagenetic and/or hydrothermal alteration of volcanic glass.…”

Section: Resultsmentioning

confidence: 91%

The use of Snyder synthetic hydrograph for simulation of overland flow in small ungauged and gauged catchments

Fedorova¹,

Kovář²,

Gregar³

et al. 2018

Soil & Water Res.

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Vlček V., Pospíšilová L., Uhlík P. (2018) Variations in mineralogical and elemental composition of Turbic Cryosol (King George Island and James Ross Island), Skeletic Cryosol (J. Ross Island, the Trinity Peninsula), Leptic Andosols (Deception Island), and Skeletic Andosols (Deception Island) were studied. Significant differences in mineralogical composition in size fraction, vertical and horizontal position were determined by X-ray diffraction quantitative analysis. The differences were attributed to a variable degree of chemical weathering process. As a product of weathering were defined montmorillonite, chlorite, microcrystalline polymorphous silica, Fe oxides, and oxyhydroxides. Their content was increased towards the surface and in a finer fraction. Crystal thickness and size distribution of montmorillonite was measured by the Bertaut-Warren-Averbach technique and the results confirmed higher intensity of chemical weathering in Turbic Cryosols (J. Ross Island and King George Island). Feldspars and volcanic glass were the main phases found in soil samples from Deception Island. They were determined as phases of parent rock and indicated low intensity of chemical weathering. Clinoptilolite was identified in soil samples from J. Ross Island and Deception Islad and its hydrothermal origin was supposed. Soil (sample AP) from Base General Bernardo O'Higgins Riquelme had significantly higher content of phosphate minerals, which was a result of ornithogenic activities. Macro elements content was consistent with mineralogical analyses. Turbic Cryosols were rich in iron, aluminium, magnesium, and manganese (> 2%). Skeletic Cryosols contained also iron, aluminium, magnesium, manganese, calcium, and sulphur (> 1%). Leptic Andosols were rich in iron and aluminium (> 2%). Soil properties and humic substances quality were evaluted. Results of chemical and physical analyses indicated that poorly developed soils of Antarctica varied in acidity, conductivity, humus content, and texture. Humic substances content and quality were low. Mainly mechanical (physical) and chemical weathering processes played major role in the soil development accompanied by low intensity of biological activity.

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“…Overall, the specific layered structure of smectites is responsible for their unique properties, such as high CEC and TSSA, swelling capacity, low hydraulic conductivity and high adsorption capacity. Due to these properties, smectites have been studied for many potential environmental applications, for example, as sealing material in landfill liners (Andrejkovičová et al 2008), backfill material for construction of high-level nuclear waste (HLW) repositories (Pacovský et al 2007;Stríček et al 2009;Osacký et al 2013), wastewater treatment (Viraraghavan & Kapoor 1994), adsorbent for heavy metals (Sheta et al 2003;Rao et al 2006;Andrejkovičová et al 2010;Galindo et al 2013) and organic compounds (Tiller et al 1984). The bulk of the world's bentonite production in 2018 (~28 million t) is used as pet waste absorbents, drilling mud, foundry sand and ore pelletizing (U.S. Geological Survey 2019).…”

Section: Introductionmentioning

confidence: 99%

Mineralogical and physico–chemical properties of bentonites from the Jastrabá Formation (Kremnické vrchy Mts., Western Carpathians)

Osacký

Binčík

Paľo

et al. 2019

Geologica Carpathica

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In the past years an increasing demand for bentonites resulted in the opening of new bentonite deposits in the Jastrabá Formation. The shortage of information, in particular analytical data, on the bentonites from the newly opened Jastrabá Fm. deposits was the motivation for the current study. Smectite is the predominant mineral in all bulk bentonites from the new deposits. Its amount varied between 43 and 90 wt. %. The bulk bentonites also contain variable amounts (10–57 wt. %) of mineral admixtures such as feldspars, mica, opal-CT, kaolinite, quartz and sometimes goethite. The smectite mineral comprising the studied bentonites was montmorillonite. The octahedral Al in the structure of montmorillonite was partially substituted by Mg, and to a lesser extent by Fe. The interlayer space of montmorillonite is occupied predominantly by divalent exchangeable cations (Ca2+ and Mg2+). The dehydroxylation temperature of smectites (>600 °C) determined on the DTG curves indicates the presence of the cis-vacant variety of montmorillonites. The mean crystallite thicknesses of smectites (TMEAN) calculated by BWA analyses ranges from 7.2 to 11.5 nm. The shape of the crystallite thickness distributions (CTDs) for smectites is lognormal in all cases. Cation exchange capacity (CEC) and total specific surface area (TSSA) increases with increasing amount of smectite. The CEC of 101 meq/100g and TSSA of 616 m2/g correspond to bulk bentonite from the Stará Kremnička III deposit containing 89 wt. % of smectite.

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Mineral stability of Fe-rich bentonite in the Mock-Up-CZ experiment

Cited by 19 publications

References 23 publications

Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite—The Initial State and the State following Thermal Treatment at 200 °C

Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite—The Initial State and the State following Thermal Treatment at 200 °C

The use of Snyder synthetic hydrograph for simulation of overland flow in small ungauged and gauged catchments

Mineralogical and physico–chemical properties of bentonites from the Jastrabá Formation (Kremnické vrchy Mts., Western Carpathians)

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