Kinetics of Alkaline Leaching of UO2 and FeS2 in Co-existing System

Abstract

The dissolution of uranium dioxide under oxidative alkaline conditions is critically influenced by iron pyrite (FeS2), which is a gangue mineral commonly found in uranium ores. This paper makes an effort in understanding the kinetics of dissolution of UO2 in a co-existing system of UO2 and FeS2 under the lixiviant combination of Na2CO3 and NaHCO3–O2 at elevated temperature and pressure. Dissolution experiments were carried out in a laboratory batch autoclave reactor using synthetic mixtures of minerals consisting of UO2, FeS2 (reactive gangue—varied from 1 to 6 %), silica (inert gangue) and calcite (inert gangue). The kinetic profiles indicated that the rate of dissolution of UO2 increased with initial increase in FeS2 content in the feed and decreased when the FeS2 weight increased beyond 3 %. The dissolution phenomenon was analysed using scanning electron microscopy and X-ray diffraction studies.