Oxidative leaching kinetics of U(IV) deposit under acidic oxidizing conditions

• Oxidative leaching of U(IV) deposit is studied and its kinetics is controlled by the diffusion through the product layer.
• Activation energy of the process is 22.803 kJ/mol.
• The kinetic model for leaching uranium from U(IV) deposit is expressed as 1−2/3X−(1−X)2/3=3.34d0−2[H2SO4]1.073[H2O2]2.084exp(−22,803/RT)t.

Oxidative leaching kinetics of U(IV) deposit in dilute H2SO4 solution with H2O2 as oxidizing agent has been investigated. The kinetics results showed that, the rate is controlled by diffusion through the “product” layer composed of the associated concomitants. The leaching process follows the kinetic model 1 − 2/3X − (1 − X)2/3 = kt with an apparent activation energy of 22.803 kJ/mol. It was found that both sulfuric acid and hydrogen peroxide have significant effects on the leaching rate of uranium species. The reaction orders of H2SO4 and H2O2 were determined as 1.073 and 2.084, respectively. It is also found that particle size presents a clear effect on uranium leaching rate, and the rate constant (k) is proportional to d−2. The kinetic model for leaching uranium from U(IV) deposit is expressed as 1−2/3X−(1−X)2/3=3.34d0−2[H2SO4]1.073[H2O2]2.084exp(−22,803/RT)t which coincided with the experimental results.