Batch Simulation of Multistage Countercurrent Extraction of Uranium in Yellow Cake from Monazite Processing with 5% TBP/Kerosene

Abstract

In the processing of monazite ore to separate uranium, thorium and rare earth elements composed in the ore, uranium is first extracted and precipitated in the form of sodium diuranate (Na2U2O7) or yellow cake. This yellow cake requires further purification to remove thorium and traces of rare earth impurities from the cake. The extraction of uranium in 4N HNO3 with 5% TBP/kerosene extractant has been studied with a series batchwise extraction to simulate multistage countercurrent solvent extraction. Feed solutions were prepared from yellow cake obtained from the processing of monazite ore which has about 60% purity of uranium. Simulated continuous countercurrent extraction with 4, 5 and 6 extraction stages were carried out. Equilibrium distribution coefficients (D) of both uranium and thorium were found to decrease with increasing feed concentration and distribution coefficient of uranium is about 8.8 to 10.8 times higher than that of thorium. The highest distribution coefficient of uranium is 3.107 at uranium concentration of 3,182mg/L. Uranium recovery was found to increase from 83.76 to 90.91% with the increasing number of extraction stage from 4 to 5. Increasing of solvent to feed ratio from 1:1 to 2:1 also increases uranium recovery from 83.76 to 93.30%. However, purity of uranium obtained from most extraction seems to be limited at 93-94%. This suggests that a scrubbing process will be required to improve the purity of uranium in this extraction system.