Naslov
Tetrahedral charge of bentonites from Croatia and neighbouring countries

Autori
Gott, Filip ; Gverić, Zvonka ; Hanžel, Darko ; Kampić, Štefica ; Tibljaš, Darko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
6th Croatian Geological Congress Abstracts Book / Horvat, Marija ; Matoš, Bojan ; Wacha, Lara - Zagreb, 2019, 79-79

Skup
6. hrvatski geološki kongres s međunarodnim sudjelovanjem

Mjesto i datum
Zagreb, Hrvatska, 09.10.2019. - 12.10.2019

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
bentonite, tetrahedral charge, Croatia

Sažetak
Bentonites as important industrial minerals have versatile industrial applications. The applications depend on their mineralogical, structural and chemical characteristics. One of such properties is the location of charge that can originate from substitutions either in the tetrahedral or octahedral layer. Therefore, this study was focused on tetrahedral charge determination of 12 bentonite samples, from 10 localities in Croatia and neighbouring countries, that were already the subject of earlier investigations e.g. GVERIĆ et al. (2018). Locations of samples are the following: Bednja, Bunarić, Divoselo, Draga, Lončarski Vis, Paripovac, Poljanska Luka and Sjeničak (Croatia) ; Šipovo (Bosnia and Herzegovina) ; Vranjska Banja (Serbia). In earlier research chemical composition (ICP/AES and ICP/MS) and mineral composition (XRD and IR) were determined. Thermal analyses and CEC determination had been made as well. Earlier investigations showed discrepancies between layer charge determined by chemical formulae calculations using chemical analysis data and those determined experimentally by observing the swelling behaviour of potassium saturated samples solvated with ethylene glycol. In order to better define their layer charge, especially the tetrahedral one, additional analyses were done. Percent of tetrahedral charge was determined by slightly modified procedure of KAUFHOLD et al. (2017), namely by measuring the CEC (copper ethylenediamine complex method) before and after treatment with 1.5 M LiCl solution. During the heating of Li-saturated samples, Li migrates within the structure to compensate for octahedral charge deficiency, therefore the CEC measured after Li saturation is a result of tetrahedral charge only. Full width at half maximum (FWHM) of d001 reflection of Cudien-exchanged bentonites was also determined since it is known that it is correlated with tetrahedral charge (KAUFHOLD et al., 2011). Additionally iron (II) content (FeO), which can influence layer charge values obtained by chemical formulae calculations, was determined by Mössbauer spectroscopy and Wilson method (WILSON, 1955). Tetrahedral charge values, expressed in % of total charge, obtained by CEC measurements were compared to those obtained by chemical formulae calculations (Figure 1). CEC measurements showed that all of the samples, according to the classification scheme proposed by EMMERICH et al. (2009), can be classified as beidellitic montmorillonites. Chemical formulae calculation method confirmed the dominance of beidellitic montmorillonites among investigated samples. There are to exceptions ; one of the samples should be classified as montmorillonitic beidellite while another should be classified as beidellite. Performed analyses (both methods) showed that Fe (II) is absent or present in very low quantities (in <2µm fraction up to 0.91 wt% FeO which corresponds to 15.3% of total Fe).

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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