Kinetics and Mechanism of Thermal Decomposition of Uranyl Oxalate

Abstract

Uranyl oxalate was prepared and its thermal decomposition in argon environment was studied using TGA, DTA, DSC and quadrupole mass analyzer. It was observed that uranyl oxalate decomposed into mixture of U₃O₈ and UO_2.13 with the evolution of carbon monoxide, oxygen and carbon dioxide in the temperature range of 573-673 K. But beyond this temperature U₃O₈ and UO_2.13 appeared as intermediate and the final product was found to be UO_2.12. This solid state decomposition was found to obey AE4 mechanism represented by the kinetic equation k × t = [-ln (1 - a)]^3/4. The activation energy of the reaction was found to be 824.83 kJ/mol. The heat of reaction and the entropy of the reaction were found to be 832.2 kJ/mol and 902.0 J/K/mol, respectively.