Processing of Monazite Mineral Concentrate for Selective Recovery of Uranium

Abstract

A procedure for selective recovery of uranium from a hydrous oxide cake produced after alkali breakdown of Rosetta monazite mineral concentrate was proposed. This procedure was based on using urea as a leaching and chelating agent. The proposed procedure involved selective leaching of uranium (98%) using 150 g/L urea within 5 h agitation time, 400 rpm agitation speed at 25 °C and solid/liquid (S/L) ratio of 1/4 (weight/volume), leaving behind thorium (Th) and rare earth elements (REEs) content. Kinetics of leaching process as well as reaction mechanism between urea and uranium has been discussed. The results show that the predominant dissolution mechanism of uranium was chemically controlled and the apparent activation energy was 45.103 kJ/mole. The work was then shifted to separate Th selectively from the combined Th–REEs hydroxide cake via alkali dissolution of Th using a mixed weight of 3/1 Na2CO3/NaHCO3 in a total concentration of 150 g/L. Finally, a tentative flow-sheet for selective recovery of U, Th and REEs from the studied hydrous oxide cake was presented.