Gangue–reagent interactions during acid leaching of uranium

During the acid leaching of uranium, gangue–reagent interactions have both negative and positive consequences. Gangue dissolution increases reagent costs, and in some cases can prevent the economic acid leaching of an ore, but can also increase uranium mineral exposure and improve recoveries. Due to rapid dissolution kinetics, the acid consumption characteristics of the various carbonate species are readily predicted, however the same is not true of silicate gangue. Due to factors including slower leach rates, incongruent dissolution, parabolic kinetics, and surface area, pH and temperature dependence, the gangue acid consumption characteristics of silicate minerals are significantly more complex. A detailed mineralogical investigation and acid leach tests were conducted on sandstone-hosted uranium ore samples. The dissolution characteristics of the more common gangue phases were determined. The study demonstrated that gangue–reagent interactions can be predicted from mineralogical data, thus reducing technical risk during processing.