Fe microenvironments in heat treated rare-earth exchanged montmorillonites
- PDF / 1,238,629 Bytes
- 7 Pages / 439.37 x 666.142 pts Page_size
- 56 Downloads / 190 Views
Fe microenvironments in heat treated rare-earth exchanged montmorillonites Erno Kuzmann 1 & Eszter M. Kovács 2 & Zoltan Homonnay 1 & Szabolcs Csákvári 1 & Zoltan Klencsár 3 & Peter Kónya 4 & Noemi M. Nagy 2 & Jozsef Kónya 2
# The Author(s) 2019
Abstract The rare-earth bentonites were prepared from Ca-bentonite by suspending Ca-bentonite in rare-earth (Ce, La, Y) perchlorate solution. 57Fe Mössbauer spectra of rare earth montmorillonites before heat treatments showed a doublet envelop at room temperature, reflecting dominantly Fe3+ assigned to (cis) octahedral site in the montmorillonite. At the same time, the 80 K spectra of these rare-earth exchanged montmorillonites revealed an additional magnetically split component, too, associated with iron atoms intercalated in the interlayer space. In the case of heat treated samples (250 °C, 360 °C and 500 °C for 4 h), a new doublet component associated with Fe3+ at trans octahedral site, appeared in both the 295 K and 80 K Mössbauer spectra. Powder X-ray diffractometry (XRD) measurements of the heat treated rare earth montmorillonites revealed that a gradual mineral phase transformation of montmorillonite to muscovite occurred upon the applied heat treatments, being consistent with the completing electron magnetic resonance (EMR) and Mössbauer spectroscopy (MS) results. Keywords Rare earth-montmorillonite . 57Fe Mössbauer spectroscopy . Interlayer Fe . Phase transition . Electron magnetic resonance
This article is part of the Topical Collection on Proceedings of the 5th Mediterranean Conference on the Applications of the Mössbauer Effect (MECAME 2019) and 41st Workshop of the French-speaking Group of Mössbauer Spectroscopy (GFSM 2019), Montpellier, France, 19-23 May 2019 Edited by Pierre-Emmanuel Lippens, Yann Garcia, Moulay-Tahar Sougrati and Mira Ristic (†)
* Erno Kuzmann [email protected]
1
Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
2
Imre Lajos Isotope Laboratory, Department of Physical Chemistry, University of Debrecen, Debrecen, Hungary
3
Centre for Energy Research, HAS, Budapest, Hungary
4
Geological and Geophysical Institute of Hungary, Budapest, Hungary
87
Page 2 of 7
Hyperfine Interactions
(2019) 240:87
1 Introduction Mössbauer spectroscopy has already been successfully applied to show the incorporation of Fe ion into the interlayer space of montmorillonites [1, 2]. An unexpected magnetically split component was observed in the 57Fe Mössbauer spectra of certain rare earth (e.g. La, Ce, Gd) cation exchanged montmorillonites at 78 K [3, 4] indicating Fe ions moving from their octahedral site into the interlayer space. Our present aim is to study the effect of heat treatment of rare earth montmorillonites on the variation of iron microenvironments by the help of 57Fe MS, XRD, EMR and X-ray fluorescence (XRF) methods.
2 Experimental The original Ca-montmorillonite collected in the region of Istenmezeje, Hungary. Elemental analysis of the original Ca-bentonite resulted in the following composition: 73.29% SiO2, 18.71% A
Data Loading...
