Thermodynamics and Kinetics Study on the Reactive Crystallization Process of Cerium Oxalate.

As one of the most representative rare-earth materials, cerium dioxide has been widely applied in various fields, with its quality primarily controlled by the crystallization behavior of its precursors. In this study, the thermodynamic and kinetic mechanisms governing the reaction crystallization process of cerium oxalate were systematically elucidated. First, the solubility data of cerium oxalate in water and different nitric acid concentrations at various temperatures were determined, followed by fitting using the Apelblat models. The results indicate that the solubility increases with rising acidity. Based on the obtained solubility data, the online detection laser technology with Everyview100 was employed to further investigate the metastable zone width (MSZW), which exhibits a nonmonotonic relationship with temperature, while showing an overall expanding trend with increasing stirring rates and feed rates. High cerium nitrate concentrations could broaden the MSZW, likely because of viscosity-induced limitations on molecular diffusion. In addition, the crystallization kinetics were investigated using a batch dynamic method. By employing a classical particle population balance model, the nucleation and growth rate equations of cerium oxalate were derived through regression analysis, revealing that the nucleation rate exhibits high sensitivity to supersaturation.