Microbial redox reaction of uranium; Effects of organic acids

Onuki, Toshihiko; Suzuki, Yoshinori; Nankawa, Takuya ; Kozai, Naofumi   ; Francis, A. J.*

We have examined the biological reduction of U(VI) complexed with organic acids of oxalic, tartaric, citric, and EDTA using S. putrefaciens. In biological system, the media containing lactic acid alone, concentration of the dissolved uranium decreased with time, and the precipitates were observed. The SEM and XANES analyses showed that the precipitates contained U, and its oxidation state was IV. In the other media containing oxalic, tartaric, citric, and EDTA, the concentration of dissolved uranium was almost the same as the initial one. The UV-vis spectra showed that dissolved U formed U(IV)-organic complexes in the medium containing oxalic, tartaric, citric acid or EDTA. These results suggest that the reduction of UVI by S. putrefaciens is affected by the organic acid present in the solution.