Incorporation of Uranium into Hematite during crystallization from ferrihydrite.
Incorporation of Uranium into Hematite during crystallization from ferrihydrite.
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DOI：
10.1021/es500212a
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发表时间：
2014-04-01
影响因子：
11.4
通讯作者：
Shaw, Samuel
中科院分区：
文献类型：
--
作者：
Marshall, Timothy A.;Morris, Katherine;Law, Gareth T. W.;Livens, Francis R.;Mosselmans, J. Frederick W.;Bots, Pieter;Shaw, Samuel
将水合铁暴露于含铀(VI)的水泥渗滤液(pH 10.5)中，老化以诱导赤铁矿结晶。化学萃取、透射电子显微镜和X射线吸收光谱技术的结合首次提供了证据，表明吸附的U(VI)(≈3000ppm)在高铁水合物聚集和结晶早期阶段被结合到赤铁矿中，并在赤铁矿成熟过程中继续吸收。对EXAFS和XANES数据的分析表明，U(VI)取代了Fe(III)形成了扭曲的八面体配位。EXAFS的拟合显示，铀酰键从1.81延长到1.87ä，而以前的研究表明，铀酰键在结合到赤铁矿中后完全消失。这项研究的结果既提供了对铀融入赤铁矿的新的机理理解，也确定了矿物结构中铀的键合环境的性质。通过将U(VI)固定在赤铁矿中，对于限制自然和工程环境中的铀迁移具有明显而重要的意义。
Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite. The results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments.
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