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首页> 外文期刊>Environmental Science & Technology >Formation of a U(VI)-Persulfide Complex during Environmentally Relevant Sulfidation of Iron (Oxyhydr)oxides
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Formation of a U(VI)-Persulfide Complex during Environmentally Relevant Sulfidation of Iron (Oxyhydr)oxides

机译：在环境相关的铁氧化物的硫化过程中，U（VI）-过硫化物的形成

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摘要

Uranium is a risk-driving radionuclide in both radioactive waste disposal and contaminated land scenarios. In these environments, a range of biogeochemical processes can occur, including sulfate reduction, which can induce sulfidation of iron (oxyhydr)oxide mineral phases. During sulfidation, labile U(Vl) is known to reduce to relatively immobile U(IV); however, the detailed mechanisms of the changes in U speciation during these biogeochemical reactions are poorly constrained. Here, we performed highly controlled sulfidation experiments at pH 7 and pH 9.5 on U(VI) adsorbed to ferrihydrite and investigated the system using geochemical analyses, X-ray absorption spectroscopy (XAS), and computational modeling. Analysis of the XAS data indicated the formation of a novel, transient U(Vl)—persulfide complex as an intermediate species during the sulfidation reaction, concomitant with the transient release of uranium to the solution. Extended X-ray absorption fine structure (EXAFS) modeling showed that a persulfide ligand was coordinated in the equatorial plane of the uranyl moiety, and formation of this species was supported by computational modeling. The final speciation of U was nanoparticulate U(PV) uraninite, and this phase was evident at 2 days at pH 7 and 1 year at pH 9.5. Our identification of a new, labile U(VI)-persulfide species under environmentally relevant conditions may have implications for U mobility in sulfidic environments pertinent to radioactive waste disposal and contaminated land scenarios.
机译：铀在放射性废物处置和受污染的土地中都是危险的放射性核素。在这些环境中，可能发生一系列生物地球化学过程，包括硫酸盐还原，这可能会导致氧化铁（羟基氧化物）矿相发生硫化。在硫化过程中，不稳定的U（VI）会还原为相对不动的U（IV）。然而，在这些生物地球化学反应过程中U形态变化的详细机制受到的约束很有限。在这里，我们对吸附在三水铝石上的U（VI）进行了pH值为7和9.5的高度受控的硫化实验，并使用地球化学分析，X射线吸收光谱（XAS）和计算模型研究了该系统。对XAS数据的分析表明，在硫化反应过程中，有一种新型的，瞬态的U（Vl）-过硫化物作为中间物种形成，伴随着铀向溶液中的瞬时释放。扩展的X射线吸收精细结构（EXAFS）建模表明，过硫化物配体在铀酰部分的赤道平面上是配位的，并且该物种的形成得到了计算建模的支持。 U的最终形态为纳米颗粒U（PV）尿素，在pH为7的第2天和pH 9.5的1年时，这一阶段很明显。我们在与环境有关的条件下识别出一种新的不稳定的U（VI）-过硫化物物种，可能会对与放射性废物处置和受污染土地情景有关的硫化环境中的U迁移产生影响。

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    《Environmental Science & Technology》 |2020年第1期|129-136|共8页
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    Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science Department of Earth and Environmental Sciences;

    School of Chemistry;

    School of Chemistry Photon Science Institute The University of Manchester Manchester M13 9PL U.K.;

    Diamond Light Source Ltd. Diamond House Harwell Science and Innovation Campus Didcot Oxfordshire 0X11 ODE U.K.;

    Radioactive Waste Management Didcot Oxfordshire OX 11 ORH U.K.;

    Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science Department of Earth and Environmental Sciences School of Chemistry;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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