Kinetic studies on the thermal decomposition of phosphate-doped sodium oxalate

Abstract

The thermal decomposition kinetics of sodium oxalate (Na 2 C 2 O 4 ) has been studied as a function of concentration of dopant, phosphate, at five different temperatures in the range 783-803 K under isothermal conditions by thermogravimetry (TG). The TG data were subjected to both model-fitting and model-free kinetic methods of analysis. The model-fitting analysis of the TG data of all the samples shows that no single kinetic model describes the whole a versus t curve with a single rate constant throughout the decomposition reaction. Separate kinetic analysis shows that Prout-Tompkins model best describes the acceleratory stage of the decomposition, while the decay region is best fitted with the contracting cylinder model. Activation energy values were evaluated by both model-fitting and model-free kinetic methods. The observed results favour a diffusion-controlled mechanism for the thermal decomposition of sodium oxalate.