Effect of Ca(II) additive on the thermal dehydration kinetics of cerium oxalate rods

Abstract

Kinetics of the thermal dehydration of solid-state reaction between cerium oxalate microrods and calcium oxalate has been studied using non-isothermal TG–DTA technique. With the introduction of calcium oxalate in varying compositions, the diffusional removal of the incorporated water molecules is impeded due to the blocking action of the surface product layer and the interaction of Ca(II). The procedure of kinetic deconvolution is used as a tool for identifying the partially overlapped kinetic processes of the thermal dehydration of pure and mixed oxalates. Mixed oxalates take more complex reaction pathways for the dehydration rather than pure oxalates of calcium and cerium. The thermal dehydration of pure cerium oxalate decahydrate and calcium oxalate dihydrate occurs in two stages, whereas that of mixed oxalates occurs in three stages. The amount of activation energy needed for the removal of 10 molecules of water from pure cerium oxalate rods and its mixture with calcium oxalate was determined by the isoconversional methods such as KAS, FWO and iterative isoconversional procedure. Significant effect in the thermal stability was observed for the compositions containing lower mass% of calcium oxalate. The average values of \(E_{{{\text{a}}_{\text{i}} }}\) for each independent process of the thermal dehydration of the mixed oxalates follow the order CC4 < CC3 < CC2.