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Non-isothermal decomposition kinetics of gibbsitic bauxite from thermogravimetric data
Published in Verlag Schmidt GmbH
Volume: 62
Issue: 2
Pages: 120 - 125
A comprehensive study to determine the thermal decomposition kinetics of naturally occurring high aluminous bauxite rock with variation of heating rate is of absolute necessity to better understand the underlying mechanism so that the course of the reaction, optimization of process conditions, and the nature of the end product can be carefully controlled. The kinetics of thermal decomposition of gibbsitic bauxite were studied by thermogravimetric analysis (TG) in static air using different heating rates (5.0, 7.5 and 10.0 K.min -1) under non-isothermal conditions. The isoconversional Flynn-Wall-Ozawa and model free Kissinger methods were applied to determine the kinetic activation energy and pre-exponential factor parameters of the decomposition process. The bauxite decomposed by two steps. The 1st step consisted of transformation through a dehydration process from bauxite to boehmite in the temperature range 275-350 °C. This was followed by a 2 nd step conversion into pseudo boehmite or metastable transition alumina through removal of structural water from the boehmite crystal lattice in the temperature range 450-550 °C. The average activation energy computed by both methods was found to be well consistent with values from other reference sources. Finally, the Malek method was employed to elucidate appropriate model expression for the thermal decomposition mechanism of the bauxite.
About the journal
JournalInterCeram: International Ceramic Review
PublisherVerlag Schmidt GmbH