Bioleaching of a Spanish uranium ore

Abstract: The bioleaching of a low-grade uranium ore in shaker and columns using natural, pure and mixed cultures has been studied. Initially, a chemical and microscopical characterization of the mineral was carried out. Orbital shaker experiments were performed to quickly obtain the best bacterial leaching conditions. Afterwards, small columns were used to determine other variables related to percolation leaching. Finally, an uranium ore from the F6 mine (Ciudad Rodrigo, Spain) was leached in the presence of bacteria using large columns (24 cm diameter and 275 cm height). The most important results were: (i) the ore contains sufficient pyrite in order for uranium bioleaching to take place under optimum conditions; (ii) shaker experiments showed that temperature, pH and type of inoculum are the most important variables in bioleaching; (iii) two different ores were attacked in the columns: altered and non-altered. In the first case, the extraction rate of uranium was higher. However, in both cases the final efficiency was very similar (95%).