Bibliographic Details
| Title: |
Biogenic Formation and Growth of Uraninite (UO2). |
| Authors: |
SEUNG YEOP LEE1 seungylee@kaeri.re.kr, MIN HOON BAIK1, JONG WON CHOI1 |
| Source: |
Environmental Science & Technology. 11/15/2010, Vol. 44 Issue 22, p8409-8414. 6p. |
| Subject Terms: |
Uraninite, Nanocrystals, Clustering of particles, Shewanella putrefaciens, Iron bacteria, Radioactive waste characterization, Environmental chemistry techniques, Transmission electron microscopy |
| Abstract: |
Biogenic UO2 (uraninite) nanocrystals may be formed as a product of a microbial reduction process in uranium-enriched environments near the Earth's surface. We investigated the size, nanometer-scale structure, and aggregation state of UO2 formed by iron-reducing bacterium, Shewanella putrefacians CN32, from a uranium-rich solution. Characterization of biogenic UO2 precipitates by high-resolution transmission electron microscopy (HRTEM) revealed that the UO2 nanoparticles formed were highly aggregated by organic polymers. Nearly all of the nanocrystals were networked in more or less 100 nm diameter spherical aggregates that displayed some concentric UO2 accumulation with heterogeneríy. Interestingly, pure UO2 nanocrystals were piled on one another at several positions via UO2-UO2 interactions, which seem to be intimately related to a specific step in the process of growing large single crystals. In the process, calcium that was easily complexed with aqueous uranium(VI) appeared not to be combined with bioreduced uranium(IV), probably due to be lower binding energy. However, when phosphate was added to the system, calcium was found to be easily associated with uranium(IV), forming a new uranium phase, ningyoite. These results will extend the limited knowledge of microbial uraniferous mineralization and may provide new insights Into the fate of aqueous uranium complexes. [ABSTRACT FROM AUTHOR] |
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| Database: |
GreenFILE |
