Clays and Clay Minerals, Vol. 56, No. 6, 645–654, 2008.
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Authors
Petit, S.
Righi, D.
Decarreau, A.
Issue Date
2008
Type
Article
Language
Keywords
Periodicals , Geology , Cation Exchange Capacity , Hofmann-Klemen , Kerolite , Li+ , NH4+ , Octahedral Charge , Sauconite , Smectite , Stevensite , Synthesis , Zinc
Alternative Title
Transformation Of Synthetic Zn-stevensite To Zn-talc Induced By The Hofmann-klemen Effect
Abstract
Stevensite-like sauconite, with the general composition: Si4 (Zn3-x&x)O10(OH)2R+ 2x, where & is a vacant site, was synthesized. The objective was to study the possible migration of some cations (Li+ and Zn2+) within such trioctahedral smectites, under heating, following the so-called ‘Hofmann-Klemen’ (HK) effect. The initial gel wasdivi ded into five aliquots and placed in teflon-coated hydrothermal reactorswit h distilled water, and these were hydrothermally treated at 80, 100, 120, 150, and 200ºC, respectively, over 30 days. X-ray diffraction (XRD) analysis confirmed that the samples synthesized were smectites. The number of vacant sites (x) per half unit cell (O10(OH)2) ranged from nearly 0 to 0.23 but no simple relationship was established between x and the temperature of synthesis. The samples were Li+- and Zn2+- saturated, and heated overnight at 300ºC (HK treatment). Cation exchange capacity measurements were made by Fourier transform infrared spectroscopy (FTIR) on NH4 +-saturated samples. After LiHK treatment, the structural formula of samples could be expressed as: Si4Zn(3-x)LixO10(OH)2NH4 + x , while after ZnHK treatment, it could be expressed as: Si4Zn3O10(OH)2. Analysis by XRD and FTIR showed that the samples moved from a Zn-stevensite-like structure to Zn-talc-like structure after treatment with ZnHK. These results are interpreted ase vidence that Zn2+ (and Li+) migrated into the previously vacant sites under HK treatment.
Description
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Citation
Clays and Clay Minerals, Vol. 56, No. 6, 645–654, 2008.
Publisher
The Clay Minerals Society
License
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