Autoclave leaching of refractory uranium minerals

Hydrometallurgy is the predominant process route used for the recovery of uranium values from its ores and leaching is the critical step amongst the various unit operations involved. Although simple uranium minerals like uraninite and pitchblende are readily leached with acid or alkali leachants under atmospheric pressure conditions, however refractory phases of uranium are very difficult for dissolution. In addition, some uranium ores yield low leach recovery due to the physical nature of uranium mineralization. Autoclave circuits have been proven as reliable unit processes that increase leach efficiencies resulting in stabilized and environmentally least harmful leach residues. Sustained R & D efforts in BARC have resulted in possibility of applying autoclave-leaching for the dissolution of uranium from refractory minerals (viz. betafite, liandratite) and ores with extremely fine dissemination of uranium phases, using both acid and alkaline leaching technology. An overview of these results is discussed in this paper.