Abstract Details
| Molecular- and Nano-scale Structure and Reactivity of Biogenic Uranium(IV) Oxide | |
|---|---|
| Abstract ID | W_EXAFS-10 |
| Presenter | Eleanor Schofield |
| Presentation Type | EXAFS Workshop - SSRL |
| Full Author List | E. J. Schofield (1) , J. R. Bargar (1) , S. Webb (1) , A. Mehta (1) , R. Bernier-Latmani (2) , J. O. Sharp (2) , H. Veeramani (2) , K. Ulrich (4) , D. Giammar (4) , E. Ilton (5) , S. D. Conradson (3) , D. L. Clark (3) |
| Affiliations | (1) Stanford Synchrotron Radiation Laboratory (2) Ecole Polytechnique Fédérale de Lausanne (3) Los Alamos National Laboratory (4) Washington University (5) Pacific Northwest National Laboratory |
| Category | Environmental Science |
| Abstract | Bioremediation has been proposed and extensively researched as an in-situ immobilization strategy for uranium contamination in the subsurface with nanoparticulate uraninite (UO2) being the commonly reported product. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and disordered and capable of structurally incorporating common ground water cations. In addition, it has been predicted that the nanoparticulate form would induce strain and dramatically increase the solubility.
In this study, the local-, intermediate and long-range atomic and nano-scale structure of biogenic UO2 (formed at varying pH and divalent cation concentration, using Shewanella oneidensis strain MR-1) was characterized using EXAFS, SR-based powder diffraction and TEM. The lattice parameter of the nanoparticulate phase is seen to be consistent with bulk UO2. There is no evidence for hyperstoichiometry or strain of the particles, the latter indicating that surface energy is relatively modest. Similar results are being found for other metal reducing bacteria. In agreement with the structural analysis, the surface-area normalized dissolution rate of the biogenic UO2 was found to be comparable to that of coarser, synthetic UO2.00. Mn2+ was found to attenuate the particle size of bacteriogenic UO2+x and to be structurally incorporated. This finding suggests that ground water composition can have a pronounced impact on the structure and properties of bacteriogenic uraninite. |
| Footnotes | |
| Funding Acknowledgement | |
| Molecular- and Nano-scale Structure and Reactivity of Biogenic Uranium(IV) Oxide | |
|---|---|
| Abstract ID | ENV-09 |
| Presenter | Eleanor Schofield |
| Presentation Type | Poster |
| Full Author List | E. J. Schofield (1) , J. R. Bargar (1) , S. Webb (1) , A. Mehta (1) , R. Bernier-Latmani (2) , J. O. Sharp (2) , H. Veeramani (2) , K. Ulrich (4) , D. Giammar (4) , E. Ilton (5) , S. D. Conradson (3) , D. L. Clark (3) |
| Affiliations | (1) Stanford Synchrotron Radiation Laboratory (2) Ecole Polytechnique Fédérale de Lausanne (3) Los Alamos National Laboratory (4) Washington University (5) Pacific Northwest National Laboratory |
| Category | Environmental Science |
| Abstract | Bioremediation has been proposed and extensively researched as an in-situ immobilization strategy for uranium contamination in the subsurface with nanoparticulate uraninite (UO2) being the commonly reported product. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and disordered and capable of structurally incorporating common ground water cations. In addition, it has been predicted that the nanoparticulate form would induce strain and dramatically increase the solubility.
In this study, the local-, intermediate and long-range atomic and nano-scale structure of biogenic UO2 (formed at varying pH and divalent cation concentration, using Shewanella oneidensis strain MR-1) was characterized using EXAFS, SR-based powder diffraction and TEM. The lattice parameter of the nanoparticulate phase is seen to be consistent with bulk UO2. There is no evidence for hyperstoichiometry or strain of the particles, the latter indicating that surface energy is relatively modest. Similar results are being found for other metal reducing bacteria. In agreement with the structural analysis, the surface-area normalized dissolution rate of the biogenic UO2 was found to be comparable to that of coarser, synthetic UO2.00. Mn2+ was found to attenuate the particle size of bacteriogenic UO2+x and to be structurally incorporated. This finding suggests that ground water composition can have a pronounced impact on the structure and properties of bacteriogenic uraninite. |
| Footnotes | |
| Funding Acknowledgement | |