A mössbauer spectroscopic study of aluminum- and iron-pillared clay minerals
Aouad, Amina (CNRS-Université d'Orléans CRMD)
Anastácio, Alexandre S. (University of Illinois. Department of Natural Resources and Environmental Sciences)
Bergaya, Faïza (CNRS-Université d'Orléans CRMD)
Stucki, Joseph W. (University of Illinois. Department of Natural Resources and Environmental Sciences)

Fecha:	2010
Resumen:	The placement of metal oxide pillars between clay mineral layers modifies their physicalchemical properties, including surface area, acidity, and catalytic activity. Aluminum is the most commonly used pillar cation, but theus eof Fe offers a distinct opportunity to expand therangeof catalytic behavior. The purpose of this study was to prepare Fe-pillared Laponite and montmorillonite and to characterize the resulting Fe phase(s). Laponite or montmorillonite suspension was mixed with different pillaring solutions containing Al oligomer and/or Fe oligomer with Fe:(Al+Fe) percent ratios ranging from 0 to 100%. TheAl oligomer was obtained by hydrolysis of AlCl 6HO with NaOH at pH 4. 4 and the Fe oligomer was prepared by FeCl hydrolysis with NaCO at pH 2. 2. Thepillare d clay was obtained by adding the oligomer to the clay suspension, then heating to 300°C for 3 h. The Fe oligomer and the pillared clay minerals were characterized by variable-temperature Mössbauer spectroscopy, X-ray powder diffraction, and chemical analysis. The unheated Fe oligomer was akaganeite, an Fe oxyhydroxide phase. Heating the Fe oligomer to 300°C transformed the akaganeite to hematite, but heating it in the presence of the clay protected it, at least partially, from this transformation, creating instead a phase which resembled a more poorly ordered akaganeite or a mixture of akaganeite and poorly ordered hematite. Mixing of Al and Fe oligomers in the pillaring solution had no effect on the magnetic hyperfine field of the Fe pillars, indicating that Al forms separatepill ars rather than substituting for Fein the pillar. A small fraction (4%) of the Fe pillar resisted reductive dissolution by citrate-bicarbonate-dithionite.
Derechos:	Tots els drets reservats.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Akaganeite ; Aluminum ; Iron ; Laponite ; Montmorillonite ; Mössbauer Spectroscopy ; Pillared Clay
Publicado en:	Clays and Clay Minerals, Vol. 58, Núm. 2 (2010) , p. 164-173, ISSN 1552-8367

DOI: 10.1346/CCMN.2010.0580203

10 p, 947.8 KB  Acceso restringido a la UAB

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