Thermal Analysis as a Tool for Determining and Defining Spherical Kaolinite

F. Javier Huertas1, Saverio Fiore2 and José Linares1
1 Departamento de Ciencias de la Tierra y Quimica Ambiental-Estacion Experimental del Zaidin, CSIC, Profesor Albareda, 1-18008 Granada, Spain
2 Istituto di Ricerca sulle Argille-CNR, Area di Ricerca di Potenza, PO Box 27-85050 Tito Scalo (PZ), Italy

Abstract: Samples containing spherical kaolinite, synthesized under hydrothermal conditions (T = 200 °C; t = 24 h, 192 h, 720 h) from gel with Si/Al = 0.84, were studied by differential thermal analysis/ thermogravimetry (DTA/TG) to provide a contribution to the mineralogical characterization of this unusual morphology. The data clearly show that dehydroxylation temperature of spherical kaolinite is lower than that of platy/lath kaolinite. It can also be used to detect the presence of spheres in the presence of the other morphologies. A rough estimation of its quantity can be obtained by TG data if spheres are present in appreciable concentrations. The results also confirm microscopic observations previously reported in the literature: spherical morphology is a discrete and metastable phase, and it is gradually dissolved along hydrothermal treatments of gels.

Key Words: Spherical Kaolinite • Synthesis • Thermal Analysis

Clays and Clay Minerals; August 1997 v. 45; no. 4; p. 587-590; DOI: 10.1346/CCMN.1997.0450410
© 1997, The Clay Minerals Society
Clay Minerals Society (www.clays.org)