2014 Fiscal Year Research-status Report
微生物起源Mn酸化物による放射性Csの新規固定機構の解明
| Project/Area Number |
26820410
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| Research Institution | Japan Atomic Energy Agency |
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Principal Investigator |
YU QianQian 独立行政法人日本原子力研究開発機構, 原子力科学研究部門 先端基礎研究センター, 研究員 (90712018)
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| Project Period (FY) |
2014-04-01 – 2016-03-31
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| Keywords | *Cs decontamination / biomaterial / Mn oxide / XAFS |
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| Outline of Annual Research Achievements |
The accident at the Fukushima Daiichi nuclear power plant resulted in an abruptly release of huge amounts of Cs into the environment. It is important to find a suitable material for the decontamination of Cs. Biogenic birnessite (BB)is produced from biological mineralization. It possesses a layer structure, which is very similar to mica-like minerals. Therefore, BB was used as a candidate material for the fixation of Cs from the contaminated seawater.
Using microorganisms, a series of Cs adsorbents has been successfully prepared. The structural differences in atomic scale of these biomaterials were well-characterized by X-ray absorption spectroscopy(XAFS). The metal-doped material shows a higher Mn average oxidation state compared to BB. Additionally, doping of Zn or Ni during BB crystallization enhances the formation of vacancies.
The obtained materials showed good performance for Cs uptake. Additionally, the adsorption capacity of Cs for Ni doped material is 2-3 times higher than the original one. The obtained results suggested that modified biomineral has potential for the decontamination of Cs from seawater.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The study was progressed smoothly as expected.
Preparation of biogenic Mn oxide was performed successfully. The atomic structure of the biomineral was adjusted by adding Zn or Ni during crystallization of biogenic Mn oxide. Three biogenic materials: BB, Zn doped BB, and Ni doped BB were prepared, and the structure of all materials were characterized by Mn K-edge XAFS spectroscopy. The results indicated that doping of Zn or Ni during BB crystallization enhances the formation of layer vacancies and increase the average oxidation state of Mn.
Uptake of Cs by three materials was also performed with a wide range of concentration. The Ni doped material showed 2-3 times higher uptake capacity than the original one.
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| Strategy for Future Research Activity |
1. Characterizing the fixation mechanism of Cs by biological materials.
1) Determine the coordination mechanism of Cs by XAFS spectroscopy.
2) Calculate the density as well as the affinity of sorption sites on Cs adsorbent by simulating the uptake data with sorption model.
2. Comparing the Cs decontamination efficiency of optimized biological materials with commercialized Mn oxides using simulated and real seawater.
3. Summarize all experimental and computational results obtained above to clarify the new fixation mechanism for biological material.
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| Causes of Carryover |
Several field work is scheduled in the next year, including XAFS experiment in PF, and sampling of Seawater. The remaining amount is planned to use for these purpose.
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| Expenditure Plan for Carryover Budget |
XAFS experiment in PF (three times): 126,378 yen
Sampling of Seawater: 140,000 yen
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