Thermal characterization and kinetic analysis of non-isothermal decomposition process of Bauxite red mud. Estimation of density distribution function of the apparent activation energy

Thermal characterization and kinetic analysis of non-isothermal decomposition process of Bauxite red mud were carried out using thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR). It was found that the investigated decomposition was a complex heterogeneous process, which included two main decomposition stages and one sub-stage. The overall decomposition process consisted of the series of parallel and competitive reactions, which originated from the decomposition of various chemical species and solid-state transformations. This behavior was confirmed by the appearance of different forms of density distribution functions of apparent activation energy values. Furthermore, the conversion range of 0.10 <= alpha <= 0.30, with a constant value of the apparent activation energy (146.4 kJ mol(-1)) for the second stage of the overall process, belongs to calcite decomposition, which takes place through a two-dimensional diffusion mechanism. (C) 2013 Elsevier B.V. All rights reserved.