| DOI: | 10.2172/1202823
|
| 报告号: | DOE-WSU--0005271
|
| 报告题名: | Technetium (VII) Co-precipitation with Framework Aluminosilicates |
| 作者: | Harsh, James B.; Dickson, Johnbull Otah; Pierce, Eric M.; Bargar, John
|
| 出版年: | 2015
|
| 发表日期: | 2015-07-13
|
| 总页数: | 11
|
| 国家: | 美国
|
| 语种: | 英语
|
| 英文关键词: | Technetium, rhenium, Hanford waste tanks, subsurface transport, feldspathoids, sodalite, sequestration.
|
| 中文主题词: | 沉积物
; 污染物
|
| 主题词: | SEDIMENTS
; CONTAMINANTS
|
| 英文摘要: | Technetium-99 (99Tc), a long-lived radionuclide, is one of the most widespread contaminants within the Hanford subsurface. At some depths, it is only extractable with strong acids, suggesting incorporation into a solid phase. We hypothesized that Tc may have coprecipitated with feldspathoid aluminosilicates under waste tanks that had leaked caustic solutions into the vadose zone. Our objectives were to determine if Tc could be incorporated into the feldspathoids cancrinite and sodalite and under what conditions coprecipitation could occur. Our hypothesis was that sodalite was more likely to incorporate and retain Tc. Our approach was to use known methods of feldspathoid formation in solutions resembling those in Hanford waste tanks contacting sediments in terms of major ion (Na, NO3, OH, Al(OH)4, and Si(OH)4 concentrations. In some cases, Al and Si were supplied from zeolite. We used perrhenate (ReO4) as a surrogate for pertechnetate (TcO4) to avoid the radioactivity. The major findings of this study were 1) ReO4 could be incorporated into either sodalite or cancrinite but the concentration in the solid was < 1% of the competing ion Cl, NO3, or NO2. 2) The small amount of ReO4 incorporated was not exchangeable with NO3 or NO2. 3) In sodalite, NO3 was highly preferred over ReO4 but significant Re-sodalite was formed when the mole fraction in solution (Re/Re+N) exceeded 0.8. 4) A nonlinear relation between the unit cell parameter and amount of Re incorporated suggested that a separate Re-sodalite phase was formed rather than a solid solution. 5) We determined that sodalite preference for sodalite in the presence of different anions increased with the ionic size of the competing anion: Cl < CO3 < NO3 < SO4 < MnO4 < WO4 and significant incorporation did not occur unless the difference in anion radii was less than 12%. 6) Re(VII) was not significantly reduced to Re(IV) under the conditions of this experiment and Re appeared to be a good surrogate for Tc under oxidizing conditions as both oxyanions have the same size. In conclusion, incorporation of TcO4 is unlikely in the close proximity to the tanks where sodalite is likely to form in the presence of high NO3 and other anions much smaller than TcO4. |
| URL: | http://www.osti.gov/scitech/servlets/purl/1202823
|
| Citation statistics: |
|
| 资源类型: | 研究报告
|
| 标识符: | http://119.78.100.158/handle/2HF3EXSE/41823
|
| Appears in Collections: | 过去全球变化的重建
影响、适应和脆弱性
科学计划与规划
气候变化与战略
全球变化的国际研究计划
气候减缓与适应
气候变化事实与影响
|
| File Name/ File Size |
Content Type |
Version |
Access |
License |
|
|---|
| 1202823.pdf（755KB） | 研究报告 | -- | 开放获取 | | View
Download
|
|
| Recommended Citation: | |
Harsh, James B.,Dickson, Johnbull Otah,Pierce, Eric M.,et al. Technetium (VII) Co-precipitation with Framework Aluminosilicates. 2015-01-01.
|
|
|