Microbially Mediated Stable Uranium Phosphate Nano-Biominerals

The current study investigated the behavior of biosorption, desorption, biomineralization and phase transformation of uranium by Gram-positive bacteria (D. radiodurans) and Gram-negative bacteria (E. coli) and fungi (S. cerevisiae). It was found that the three types of microorganisms all had a high accumulation ability to U(VI) in the absence of additional nutrients at pH 5, the maximum uranium accumulation quantity was around 168-248 mg/g biomass (dry weight). With the extension time from 1 d to 7 d, less uranium could be extracted by 0.1 mol/L HNO3 from the three types of microorganisms. XRD, FTIR and SEM-EDS analyses indicated that the U(VI) was absorbed on the surface of the active functional groups such as amino and hydroxyl, especially phosphoryl group which might play a key role in binding uranium and U-P nucleation and crystallization. Microbially mediated-chernikovite was present as the insoluble nano-sized lamellar crystal on the surface of D. radiodurans. and S. cerevisiae, while the amorphous uranium was observed to enter the cells of E. coli. The chernikovite would be transformed into ningyoite (50-100 nano-sized globular crystals) induced by E. coli and S. cerevisiae and Na2UO2P2O7 after hydrothermal and ashing treatment, respectively. This work offers a more effective strategy for the bioremediation of uranium contaminated water, with microbially mediated the formation of insoluble U(VI) phosphates-chernikovite and U(IV) phosphates-ningyote by in situ biomineralization and hydrothermal treatment, respectively.