Kinetics of thermal decomposition of some metal oxalates

Abstract

The thermal decomposition kinetics of oxalates of Zn^II, Ni^II and Th^IV have been studied in air by isothermal and non-isothermal thermogravimetry. The isothermal kinetic results suggest that the mechanism of decomposition of the zinc compound involves rapid nucleation followed by two dimensional growth in the acceleratory region, while in the case of thorium oxalate, the initial nucleation occurs by a chain mechanism on the surface of the reactant followed by the growth of the product from the surface towards the interior. The results on nickel oxalate could not be interpreted in an unambiguous manner. The activation energy and the frequency factor obtained from TG curves compare well with those obtained from the isothermal method. The activation energies for the dehydration of these oxalates have also been evaluated from the thermogravimetric curves.