Dissolution kinetics of zirconium dioxide in nitric acid

摘要

Dissolution kinetics of zirconium dioxide (ZrO_2) in nitric acid was investigated as a function of time, temperature, acid concentration, stirring speed, solid to liquid ratio, and surface area. The dissolution appears to be a two-stage dissolution process that is related to the changes at the solid surface; the outer layer being more susceptible to dissolution than the inner layer. The initial rate of ZrO_2 dissolution was used for the comparison studies. The dissolution of zirconium dioxide follows a pseudo-first-order rate equation. An increase in the temperature of the dissolving medium enhances the initial dissolution rate of the ZrO_2. The activation energy was found to be 43.3 kJ/mol. A probable dissolution mechanism consistent with the experimental data is suggested and the steps involved in the reaction are discussed. The results are explained in terms of a surface reaction mechanism. The effect of ultrasound on the rate of zirconium dioxide dissolution was also investigated.