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Open AccessArticle

The Nature of Laponite: Pure Hectorite or a Mixture of Different Trioctahedral Phases?

1
School of Mineral Resources Engineering, Technical University of Crete, 73100 Chania, Greece
2
Institut des Sciences de la Terre d’Orléans, CNRS, 1A Rue de la Ferollerie, 45100 Orléans, France
3
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Ave., 11635 Athens, Greece
4
BYK-Chemie GmbH, Stadtwaldstrasse 44, 85368 Moosburg, Germany
5
Lehrstuhl für Anorganische Chimie I, Universität Bayreuth, 95440 Bayreuth, Germany
6
IMPMC, Sorbonne Universités, UMR 7590, UPMC, CNRS, MNHN, IRD, 4 Place Jussieu, CEDEX 05, 75231 Paris, France
*
Author to whom correspondence should be addressed.
Deceased.
Minerals 2018, 8(8), 314; https://doi.org/10.3390/min8080314
Received: 30 June 2018 / Revised: 23 July 2018 / Accepted: 24 July 2018 / Published: 26 July 2018
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
A series of laponites and synthetic OH- and fluorinated hectorites prepared from hydrothermal and melting experiments at both industrial and laboratory scale were examined with XRD and FTIR (MIR and NIR) to determine their mineralogical composition and possible compositional heterogeneity. The end materials contained both Li- and Na-bearing phases. The industrial hydrothermal OH-smectites prepared at low temperatures consist of random mixed layer hectorite-stevensite-kerolite with about 40–50% hectorite layers, the remaining being stevensite and kerolite at roughly equal proportions. The FTIR spectra of these smectites contain, besides the main Mg3OH stretching/overtone bands at 3695–3690 and 7225–7214 cm−1, respectively, additional OH overtone bands at ~3716 and 7265 cm−1 (hydrated state). These bands might be linked to Mg2LiOH stretching modes. The melt-derived smectites are kerolite-free but still contain stevensite layers, although the preparation methods involved heating in the excess of 1000 °C. In these smectites Li might be partitioned to both octahedral and interlayer sites. Subsequent annealing of the melt-derived Mg-Li smectites caused migration of the exchangeable Li to the vacant octahedral due to the Hofmann-Klemen effect and thus decrease of the layer charge, as was indicated by the νO-D method. Hydrothermal synthesis of Mg-Li smectites at high temperature (400 °C) and pressure (1 kbar), yielded pure hectorite without stevensite or kerolite domains. View Full-Text
Keywords: hectorite; stevensite; kerolite; laponite; synthesis; smectite nanoparticles hectorite; stevensite; kerolite; laponite; synthesis; smectite nanoparticles
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Christidis, G.E.; Aldana, C.; Chryssikos, G.D.; Gionis, V.; Kalo, H.; Stöter, M.; Breu, J.; Robert, J.-L. The Nature of Laponite: Pure Hectorite or a Mixture of Different Trioctahedral Phases? Minerals 2018, 8, 314.

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