The behavior of Fe in group and acid-treated vermiculite from Santa Olalla, Spain
Maqueda, Celia (Consejo Superior de Investigaciones Científicas (Espanya). Instituto de Recursos Naturales y Agrobiologia)
Romero, Agua Santas (Consejo Superior de Investigaciones Científicas (Espanya). Instituto de Recursos Naturales y Agrobiologia)
Morillo, Esmeralda (Consejo Superior de Investigaciones Científicas (Espanya). Instituto de Recursos Naturales y Agrobiologia)
Pérez-Rodríguez, José L. (Instituto de Ciencia de Materiales de Sevilla)
Lerf, Anton (Bayerische Akademie der Wissenschaften. Walther-Meissner-Institut)
Wagner, Friedrich Ernst (Technische Universität München. Physik Department)

Fecha:	2008
Resumen:	The preparation of porous materials from clay minerals by selective leaching is of interest because it yields residues with large specific surface areas that can be used as adsorbents of contaminants or as catalysts. Grinding produces surface modifications and therefore may significantly influence the leaching behavior. The aim of this paper is to study the effect of grinding and leaching on the structure of the vermiculite from Santa Olalla, Spain, using Fe Mössbauer spectroscopy, X-ray diffraction, infrared spectroscopy, and specific surface area (S) measurements. The study shows that grinding destroys the long range order of the vermiculite, but leaves the local structure in the environment of the Fe atoms intact, at least up to a grinding time of 10 min. The Mössbauer study shows that there is no Fe in the tetrahedral sheets and that grinding does not lead to a significant oxidation of the structural Fe. Vermiculite ground for 4 min and leached with 1 M HC1 solution at 80°C over a 24 h period was decomposed to X-ray amorphous silica with a very large specific surface area (S = 720 mg) and with total pore volume of 0. 586 cm g, whereas an unground sample leached with the same acid concentration yielded a specific surface area of only 504 m g. Most of the Mg and Al are removed from the ground sample after leaching with 1 M HC1, while large percentages of FeO remain with the X-ray amorphous silica. In unground vermiculite leached with 1 M HC1, a considerable amount of vermiculite remains in the residue. A sample ground for 4 min and treated with 0. 25 M HC1 also shows the typical vermiculite Mössbauer spectrum with an Fe/Fe ratio similar to that of the unground vermiculite. The samples ground for 2 or 4 min and treated with 1 M HC1 solution have an orange color and, according to the Mössbauer spectra only Fe remains. Mössbauer spectra of these samples taken at 4. 2 K reveal the presence of akaganéite.
Nota:	Altres ajuts: CICYT/AGL-2005-0164
Derechos:	Tots els drets reservats.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Acid Leaching, Grinding ; Mössbauer Spectroscopy ; Surface Properties ; Vermiculite ; X-ray Amorphous Silica
Publicado en:	Clays and Clay Minerals, Vol. 56, Núm. 3 (2008) , p. 380-388, ISSN 1552-8367

DOI: 10.1346/CCMN.2008.0560307

9 p, 856.9 KB  Acceso restringido a la UAB

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