THERMAL AND STRUCTURAL CHARACTERIZATION OF BRAZILIAN SOUTH-EASTERN KAOLINITIC CLAYS

Souza, G. P.
Sanchez, R.
Holanda, J. N. F.

Laboratory of Advanced Materials, State University of Northern Fluminense 28013-600, Campos-RJ, Brazil

^*Author for correspondence: E-mail: [email protected]

Journal of Thermal Analysis and Calorimetry 73(1):p 293-305, 2003.

This study focuses on the thermal and structural characteristics of some Brazilian kaolinitic clays. X-ray diffraction analysis have shown that the clay samples consist mainly of kaolinite, and quartz and gibbsite as principal impurities. On heating three endothermic transformations were identified as water loss from TG-MS data within the 60–64, 268–276 and 499–503°C ranges, followed by an exothermic transformation with maximum within the 950–959°C range. The endothermic valleys can be mainly interpreted as the release of free moisture, dehydration of gibbsite and dehydroxylation of kaolinite, respectively. The exothermic peak is associated with crystallization of new phases from metakaolinite. The quantification of kaolinite (59.6–74.2%) and gibbsite (5.9–10.2%) was taken by the thermogravimetric measurements. In addition, it was also demonstrated from the thermal curves that the character of the clays from South-Eastern Brazil (Campos-RJ) is predominantly kaolinic.