Hydrothermal synthesis, between 75 and 150°C, of high-charge, ferric nontronites
Decarreau, Alain (Université de Poitiers. UMR 6532 HydrASA. CNRS/INSU)
Petit, Sabine (Université de Poitiers. UMR 6532 HydrASA. CNRS/INSU)
Martin, François (ERT 1074 CNRS Géomatériaux. LMTG-OMP-UPS-IRD. CNRS)
Farges, François (USM 201 - UMR CNRS 7160. Muséum National d'Histoire Naturelle)
Vieillard, Philippe (Université de Poitiers. UMR 6532 HydrASA. CNRS/INSU)
Joussein, Emmanuel (Université de Limoges. UMR 6532 HydrASA. CNRS/INSU)

Data:	2008
Resum:	High-charge nontronites were synthesized at 75, 90, 100, 110, 125, and 150°C from a silicoferrous starting gel with SiFeNa O. nHO Composition. This gel was oxidized in contact with air and then hydrothermally treated, for a period of 4 weeks, under equilibrium water pressure. The synthesized nontronites were similar to each other, regardless of the synthesis temperature. Their structural formula, obtained from chemical analysis, X-ray diffraction (XRD), and Fourier transform infrared (FTIR), Mössbauer, and X-ray absorption fine structure spectroscopies is: (Si Fe ) Fe O (OH)Na. A strictly ferric end-member of the nontronite series was therefore synthesized for the first time. The uncommon chemistry of the synthesized nontronites, notably the high level of Fe-for-Si substitution, induced particular XRD, FTIR, and differential thermal analysis-thermogravimetric analysis data. The ethylene glycol expandability of the synthetic nontronites was linked to their crystallinity and depended on the nature of the interlayer cation, moving from smectite to vermiculite-like behavior. As the synthesis temperature increased, the crystallinity of the synthesized clays increased. The nontronite obtained at 150°C had the 'best crystallinity', which cannot be improved by increasing synthesis time or temperature.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	FTIR Spectroscopy ; High-charge Nontronite ; Mössbauer Spectroscopy ; XAFS
Publicat a:	Clays and Clay Minerals, Vol. 56, Núm. 3 (2008) , p. 322-337, ISSN 1552-8367

DOI: 10.1346/CCMN.2008.0560303

16 p, 1.4 MB  Accés restringit a la UAB

El registre apareix a les col·leccions:
Articles > Articles de recerca
Articles > Articles publicats