Hydrothermal stability of layered silicates in neutral and acidic media : Effect on engineered-barrier safety
Alba, María D. (CSIC-Universidad de Sevilla. Departamento de QuímicaInorgánica. Instituto Ciencia de los Materiales de Sevilla)
Castro, Miguel A. (CSIC-Universidad de Sevilla. Departamento de QuímicaInorgánica. Instituto Ciencia de los Materiales de Sevilla)
Chain, Pablo (CSIC-Universidad de Sevilla. Departamento de QuímicaInorgánica. Instituto Ciencia de los Materiales de Sevilla)
Orta, M. Mar (CSIC-Universidad de Sevilla. Departamento de QuímicaInorgánica. Instituto Ciencia de los Materiales de Sevilla)
Pazos, M. Carolina (Universidad Nacional de Colombia. Laboratorio de Catálisis Heterogénea. Departamento de Química)
Pavón, Esperanza (CSIC-Universidad de Sevilla. Departamento de QuímicaInorgánica. Instituto Ciencia de los Materiales de Sevilla)

Date:	2010
Abstract:	Many environmental applications in the inorganic remediation field are based on the swelling and ion-exchange capacities of smectites, even though these can be affected by hydrothermal treatment in water and acidic media. Here a systematic study of the properties of layered silicates that could affect their hydrothermal stability at different pH is described: type of layers, octahedral occupancy, layer charge, and origin of the layer charge. The silicates studied were selected on the basis of their different characteristics associated with these properties. Kanemite (1:0 phyllosilicate), kaolinite (1:1 phyllosilicate), and pyrophyllite and talc (2:1 phyllosilicates with no-layer charge) were examined in order to determine the effect of layer structure, whereas the hydrothermal reactivity of silicates with different layer charge was analyzed by comparing the talc-hectorite-Laponite and talc-saponite-trioctahedral vermiculite series. Samples were treated hydrothermally at 300°C for 48 h in pure water and in a 0. 01 M HNO solution and the final products were analyzed by X-ray diffraction, scanning electronic microscopy, and solid-state nuclear magnetic resonance spectroscopy. All layered silicates, except for kanemite, were found to remain intact after hydrothermal treatment in water and acidic media, with only minimal short-range structural changes observed. The extent of the structural changes depended on the octahedral sheet occupancy (greater extent) and the number of isomorphic substitutions (lesser extent), both of which weaken the structure.
Note:	Altres ajuts: Junta de Andalucía (P06-FQM-02179)
Note:	Altres ajuts: DGICYT/FEDER/CTQ2007-63297
Note:	Altres ajuts: MMAMRM/300/PC08/3-01.1
Rights:	Tots els drets reservats.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Bentonite ; Engineered-barrier ; Hydrothermal Stability ; Layered Silicates
Published in:	Clays and Clay Minerals, Vol. 58, Núm. 4 (2010) , p. 501-514, ISSN 1552-8367

DOI: 10.1346/CCMN.2010.0580405

14 p, 1.4 MB  UAB restricted access

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