Bacteria Mediated Uranium Species Transformation and Immobilization Mechanism in a Phosphate-rich System

Abstract Uranium tailings without reliable anti-seepage treatment in the early years of mining and metallurgy has become a potential source of pollution. This work sought to explore the transformation and mechanism of uranium species in a bacteria and phosphate coexist system. The results showed that addition of phosphate enhanced uranium removal rate greatly in solution with the highest removal rate of 99.84%. Likewise, BCR finding displayed that residual phase in sediment samples of phytic acid group and nano-hydroxyapatite group was much higher than that of control group. XRD/SEM-EDS analyses revealed that the fugitive positions of phosphorus and uranium elements remain essentially the same on the sediment surface in the groundwater-sediment system, the appearance of more pronounced phosphorus and uranium signal peaks confirmed more U-P precipitates. Combined with XPS and BCR results, very interesting, phosphate could be complexed with hexavalent uranium to form a stable precipitate. This, to some extent, do not seem to support the view that tetravalent uranium is only stable state under reducing conditions. From this point of view, it demonstrates that bacteria can effectively mediated U-P precipitates. This also provides theoretical evidence that it succeeds efficiently in realizing the transformation of uranium from a transferable phase to a stable phase, which has a potential application value to groundwater in uranium mining areas.