|
|||||
|
|
Reduction of uranium(VI) under sulfate-reducing conditions in the presence of Fe(III)-(hydr)oxides |
|
| Authors: | RK Sani JE Amonette |
| Institution: | 1 Department of Chemical Engineering, Center for Multiphase Environmental Research, Washington State University, Dana Hall Rm 118, Pullman, WA 99164-2710, USA 2 Fundamental Science Directorate, Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, WA 99352, USA 3 Department of Microbiology, 109 Lewis Hall, PO Box 173520, Montana State University, Bozeman, MT 59717-3520, USA 4 Center for Biofilm Engineering, 366 EPS, Montana State University, Bozeman, MT 59717-3980, USA |
| Abstract: | Hexavalent uranium U(VI)] dissolved in a modified lactate-C medium was treated under anoxic conditions with a mixture of an Fe(III)-(hydr)oxide mineral (hematite, goethite, or ferrihydrite) and quartz. The mass of Fe(III)-(hydr)oxide mineral was varied to give equivalent Fe(III)-mineral surface areas. After equilibration, the U(VI)-mineral suspensions were inoculated with sulfate-reducing bacteria, Desulfovibrio desulfuricans G20. Inoculation of the suspensions containing sulfate-limited medium yielded significant G20 growth, along with concomitant reduction of sulfate and U(VI) from solution. With lactate-limited medium, however, some of the uranium that had been removed from solution was resolubilized in the hematite treatments and, to a lesser extent, in the goethite treatments, once the lactate was depleted. No resolubilization was observed in the lactate-limited ferrihydrite treatment even after a prolonged incubation of 4 months. Uranium resolubilization was attributed to reoxidation of the uraninite by Fe(III) present in the (hydr)oxide phases. Analysis by U L3-edge XANES spectroscopy of mineral specimens sampled at the end of the experiments yielded spectra similar to that of uraninite, but having distinct features, notably a much more intense and slightly broader white line consistent with precipitation of nanometer-sized particles. The XANES spectra thus provided strong evidence for SRB-promoted removal of U(VI) from solution by reductive precipitation of uraninite. Consequently, our results suggest that SRB mediate reduction of soluble U(VI) to an insoluble U(IV) oxide, so long as a suitable electron donor is available. Depletion of the electron donor may result in partial reoxidation of the U(IV) to soluble U(VI) species when the surfaces of crystalline Fe(III)-(hydr)oxides are incompletely reduced. |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ | |