Dissolution of biogenic and synthetic UO2 under varied reducing conditions.
Dissolution of biogenic and synthetic UO2 under varied reducing conditions.
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DOI：
10.1021/es800647u
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发表时间：
2008-08-01
影响因子：
11.4
通讯作者：
Giammar, Daniel E.
中科院分区：
文献类型：
--
作者：
Ulrich, Kai-Uwe;Singh, Abhas;Schofield, Eleanor J.;Bargar, John R.;Veeramani, Harish;Sharp, Jonathan O.;Bernier-Latmani, Rizlan;Giammar, Daniel E.
生物 UO2 是环境生物修复的纳米颗粒产品，其化学稳定性可能会受到颗粒表面自由能、结构缺陷和成分变异性的影响，类似于非生物 UO2+x (0 ≤ x ≤ 0.25)。本研究量化并比较了生物纳米 UO2 和合成散装 UO2.00 的固有溶解度和溶解速率常数，同时考虑了分子尺度结构。在连续流实验中，在缺氧条件下，将速率确定为 pH 值和溶解的无机碳的函数。生物和合成 UO2 固体的溶解速率在接近中性 pH 值时最低，并随着 pH 值降低而增加。生物 UO2 和合成 UO2 相似的表面积归一化率表明反应表面位点密度具有可比性。这一发现与已确定的生物源 UO2 和化学计量 UO2.00 的结构同源性一致。与无碳酸盐缺氧条件相比，溶解的无机碳使生物UO2的溶解速率加快了3个数量级。这种现象表明 U(IV) 连续表面氧化为 U(VI)，其中 U(VI) 的脱离是溶解的速率决定步骤。尽管在整个实验过程中保持还原条件，但 UO2 表面可能会被水和放射性氧化剂氧化。即使在缺氧含水层中，UO2 溶解也可能由表面 U(VI) 而不是 U(IV) 相控制。
The chemical stability of biogenic UO2, a nanoparticulate product of environmental bioremediation, may be impacted by the particles’ surface free energy, structural defects, and compositional variability in analogy to abiotic UO2+x (0 ≤ x ≤ 0.25). This study quantifies and compares intrinsic solubility and dissolution rate constants of biogenic nano-UO2 and synthetic bulk UO2.00, taking molecular-scale structure into account. Rates were determined under anoxic conditions as a function of pH and dissolved inorganic carbon in continuous-flow experiments. The dissolution rates of biogenic and synthetic UO2 solids were lowest at near neutral pH and increased with decreasing pH. Similar surface area-normalized rates of biogenic and synthetic UO2 suggest comparable reactive surface site densities. This finding is consistent with the identified structural homology of biogenic UO2 and stoichiometric UO2.00. Compared to carbonate-free anoxic conditions, dissolved inorganic carbon accelerated the dissolution rate of biogenic UO2 by 3 orders of magnitude. This phenomenon suggests continuous surface oxidation of U(IV) to U(VI), with detachment of U(VI) as the rate-determining step in dissolution. Although reducing conditions were maintained throughout the experiments, the UO2 surface can be oxidized by water and radiogenic oxidants. Even in anoxic aquifers, UO2 dissolution may be controlled by surface U(VI) rather than U(IV) phases.
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影响因子：
6.2
作者：
JOHNSON, DA;FLORENCE, TM
通讯作者：
FLORENCE, TM
影响因子：
6.2
作者：
CHRISTENSEN, H;SUNDER, S;SHOESMITH, DW
通讯作者：
SHOESMITH, DW
影响因子：
56.9
作者：
Kubatko, KAH;Helean, KB;Burns, PC
通讯作者：
Burns, PC
影响因子：
11.4
作者：
Frazier, SW;Kretzschmar, R;Kraemer, SM
通讯作者：
Kraemer, SM
影响因子：
11.4
作者：
Ginder-Vogel, Matthew;Criddle, Craig S.;Fendorf, Scott
通讯作者：
Fendorf, Scott