| Non-Isothermal Kinetic Evaluation of
Pyrophyllite Dehydroxylation |
Mostofa Shamim, Atiar Rahaman Molla1, Tapas Kumar Mukhopadhyay2 and Kausik Dana*
pages : 181-186
DOI : 10.1080/0371750X.2014.922434 |
| Abstract |
| Dehydroxylation of clay minerals is an important process with several applications. Despite the industrial use of
several well defined clay minerals, only the dehydroxylation kinetics of kaolinite has been reported. Still, the kinetics
of these solid state reactions is yet to be understood using unambiguous model. In the present work, we have
performed detailed kinetic analysis of dehydroxylation of pyrophyllite clay using non-isothermal kinetics by
thermogravimetry (TG) at different heating rates. The TG data has been analysed initially with model-free methods
(ASTM E 698, ASTM 1641, Friedman analysis and Ozawa-Flynn-Wall method). Interestingly, both the model-free
methods of analysis have unequivocally indicated that activation energy (Eact) changes very marginally with progress
of reaction and a single activation energy barrier is present. This surmises that the dehydroxylation process is a
single stage process. A multivariate non-linear regression on the dynamic thermal data at different heating rates
has been performed to determine the most probable kinetic model based on statistical fit. It has been found that,
TG data provides best fit with regression coefficient (r2) value of 0.994, when a single stage Avrami type diffusion
reaction model is assumed, and an activation energy of 159 kJ.mol–1. |
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