Microbial leaching of uranium from flotation tailings in alkaline media

Different heterotrophic microorganisms were able to leach uranium from flot ation tailings in alkaline solutions. The solubilization of uranium was car ried out by at least two different mechanisms. The first mechanism was conn ected with the microbial production of peroxide compounds which turned the tetravalent uranium to the hexavalent state. The U6+ was then solubilized a s uranyl carbonate or as complexes with some organic compounds present in t he solutions. The second mechanism was connected with the solubilization of uranium as complexes with some organic compounds, mainly organic acids, pr oduced by the microorganisms.