Rorie Gilligan

Brannerite, UTi2O6, is the most important uranium mineral after uraninite and coffinite, and the most common refractory uranium mineral. As the more-leachable ores become exhausted, it is necessary to process complex and refractory ores to meet the growing demand for uranium as an energy source. The present study was carried out to provide information that will enable the development of a more effective processing strategy for the extraction of uranium from ores containing brannerite. A detailed study was carried out to understand the leaching behaviour of brannerite in sulphate media (10–200 g/L H2SO4) under moderate temperature conditions (25–96°C), and in alternative acid and alkaline systems. The feed and the leached residues were characterised by X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry techniques. The brannerite dissolved up to 95% after 5 h leaching in ferric sulphate media, up to 89% in ferric chloride media under similar conditions, and up to 82% in 24 h in sodium carbonate media. The alkaline leaching was repeated with a high-carbonate brannerite-bearing ore, which showed comparable extractions. Mineralogical characterisation showed that altered and amorphous regions are a regular feature of brannerite, and that pitting is typically observed on the surface of the leached grains. Brannerite was shown to generally dissolve congruently, with altered and amorphous regions in the brannerite grains dissolving faster than the crystalline regions, which implies that the extent of brannerite alteration is a key parameter in the process selection, along with the grade, liberation size and gangue mineralogy.