Crystal growth and agglomeration study of uranium peroxide precipitation

International audienceIn the processing of uranium ores, crushed minerals are first leached with sulfuric acid or sodium carbonate. The liquor obtained after filtration is purified and concentrated by solvent extraction. Uranium is then recovered by precipitation as yellow cake concentrates. This selective precipitation operation is an essential step of the process as it determines the final qualities of the product. It allows a higher purity to be reached and provides solid particles that have to meet specific physical properties in terms of granulometry, morphology, density A number of different precipitating reagents such as ammonia, magnesium oxide, sodium hydroxide are industrially used, the most common being ammonium hydroxide. However, hydrogen peroxide offers the advantage to be very selective, especially from molybdenum, vanadium, sodium and phosphorus, which are important naturally occurring impurities. Furthermore, the continuous precipitation process of the uranium peroxide in fluidized bed reactor leads to high-quality solid particles regarding filtering operations, downstream handling and powder transportation. The objective of this work is to present a thermodynamic and kinetic study of the uranium peroxide precipitation which is achieved at pH ~ 3 by mixing hydrogen peroxide and uranyl sulfate solutions