A kinetic model for alkaline leaching of uranium from dolomitic limestone ore

Abstract

The choice of type of leaching to be employed in the leaching process for extraction of uranium from its ore is dictated by the chemical nature of gangue minerals rather than that of uranium minerals present in the ore. The kinetics of extraction of uranium values into aqueous phase is dependent on type of leachant chosen, uranium minerals present and their mode of occurrence. Present study is aimed to get an insight into the kinetics of alkaline leaching of uranium from an Indian uranium ore containing high carbonates, about 80%, as gangue minerals. Heterogeneous kinetic model, shrinking core with mixed surface reaction and diffusion dissolution kinetics was found to be best fitting to predict the rate of leaching. The ranges of influence of factors studied were partial pressure of oxygen from 4.5 kg/cm2 to 6.5 kg/cm2, stirring speed between 573 rpm to 900 rpm, reaction temperature in the range 125°C to 165°C and particle size from 25.8 µ to 34.76 µ. The orders of reaction with respect to partial pressure of oxygen, stirring speed, particle size and Arrhenius activation energy of uranium leaching were determined to be 2.5, 0.21, –5.7 and 4.5 kcal/mole respectively.