Effect of semiconducting metal oxide additives on the kinetics of thermal decomposition of sodium oxalate under isothermal conditions

The effect of semiconducting metal oxide (CuO and TiO2) additives on the kinetics of thermal decomposition of sodium oxalate (Na2C2O4) to sodium carbonate has been studied at five different temperatures in the range 783–803 K under isothermal conditions by thermogravimetry (TG). Irrespective of whether p- or n-type, the metal oxides show an increase in the rates of both stages of decomposition up to an oxide concentration of 1 wt% and then decreases (at higher concentrations). The TG data were subjected to model fitting kinetic methods of analysis. The rate law for the decomposition of Na2C2O4 (Prout–Tompkins and contracting cylinder models respectively for the acceleratory and decay stages) remained unaffected by the additives. Similar effects were observed with pre-compressed metal oxide additives on the thermal decomposition of Na2C2O4. The results support the diffusion controlled mechanism proposed earlier for the isothermal decomposition of sodium oxalate.