Some results of microbial leaching of Uranium ore samples from Narwapahar, Bhatin and Keruadungri, Singhbhum District, Bihar

Some samples of uraniferous chlorite-schist from Narwapahar, Bhatin and Keruadungri mines, analysing 0.032 ± 0.003% U3O8 were tested to ascertain the effects of bacteria on percolation leaching of uranium. Iron and sulphur oxidizing bacteria found to be present in these ores were separated and leaching tests on these ores carried out using 9K nutrients. It was found that percolation with the help of these bacteria and 9K nutrients increased the leachability of uranium over that obtained by simple percolation leaching without the use of bacteria. This leachability increased from 60.0 to 72.0% in case of Bhatin ore, 62.6 to 94.2% in case of Keruadungri ore, and 58.3 to 77.4% in case of Narwapahar ore with a reduction in leaching time from 12 to 8 weeks. As ferrous iron (Fe3+) is preferentially solubilized in the early stages of leaching with resultant buildup of Fe3+ ions in following stages, it is necessary to remove it as it hinders solubilization of uranium. This was done by batch withdrawal of leach liquor. This helped not only uranium solubilization but also resulted in reduction of leaching time. The sulphur reducing bacteria Desulpho-vibrio disulphuricants, though in the ore, become ineffective due to aeration of leach liquor during percolation and the presence of acidic environment produced by the addition of acid from time to time. The results of these show, in the three ores tested, that bacterial leaching technique would lead to better uranium recoveries. (M.C. Bhurat, K.K. Dwivedy, K.M.V. Jayaram and K.K. Dar, Atomic Minerals Division, New Delhi)