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Clay Minerals; March 2008; v. 43; no. 1; p. 129-135; DOI: 10.1180/claymin.2008.043.1.10
© 2008 Mineralogical Society of Great Britain and Ireland
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Spectroscopic studies of kaolin from different Brazilian regions

R. B. SCORZELLI1,*, L. C. BERTOLINO2, A. B. LUZ3, M. DUTTINE2, F. A. N. G. SILVA3 and P. MUNAYCO1

1 C.B.P.F., Rua Dr. Xavier Sigaud, 150, 22290-180 Rio de Janeiro, Brazil, 2 U.E.R.J., Rua Francisco Portela, 794. Paraíso, São Gonçalo, Rio de Janeiro, Brazil, and 3 C.E.T.E.M., Av. Ipê, 900, Ilha da Cidade Universitária, Rio de Janeiro, Brazil

* E-mail: cbertolino{at}uol.com.br

(Received 29 March 2007; revised 13 August 2007)

Over the past several decades, kaolin has been used intensively in the paper industry as a coating and filler material. These applications require kaolin of a high brightness grade, which depends heavily on the level of impurities (mainly Fe-bearing minerals such as Fe oxides and hydroxides) and may be improved by beneficiation processes involving grain-size classification, magnetic separation and chemical treatments. This investigation was carried out on five Brazilian kaolin samples of different geographical and geological origins. Granulometric, mineralogical, chemical and physical characterizations were performed on all samples before and after the beneficiation process.

Chemical compositions were determined by X-ray fluorescence and the most important crystalline phases were identified using X-ray diffraction. Kaolinite is the dominant mineralogical phase with minor amounts of muscovite and quartz. The nature of Fe impurities was investigated by electron spin resonance and 57Fe Mössbauer spectroscopy. For all studied kaolin samples, Fe ions (Fe3+ and Fe2+) are present in variable amounts, in the kaolinite structure and also in Fe oxides (magnetite, hematite and goethite). The beneficiation procedure aims to remove these Fe oxides and was found to be most efficient for the Mogi das Cruzes kaolin. The Seridó kaolin had the best whiteness index observed among the analysed samples.

KEYWORDS: kaolinite, Fe impurities, 57Fe Mössbauer spectroscopy, electron spin resonance, XRD, XRF






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