The effect of particle size on the thermal decomposition kinetics of potassium bromate

The thermal decomposition of potassium bromate (KBrO3) has been studied as a function of particle size, in the range 53-150 mu m, by isothermal thermogravimetry at different temperatures, viz. 668, 673, 678, and 683 K in static air atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of all samples of KBrO3 at all temperatures studied. The isothermal decomposition of all samples of KBrO3 was subjected to both model fitting and model-free (isoconversional) kinetic methods of analysis. Isothermal model fitting analysis shows that the thermal decomposition kinetics of all the samples of KBrO3 studied can be best described by the contracting square equation. Contrary to the expected increase in rate followed by a decrease with decrease in particle size, KBrO3 shows a regular increase in rate with reduction in particle size, which, we suggest, is an impact of melting of this solid during decomposition.