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Direct Visualization of Arsenic Binding on Green Rust Sulfate

机译：直接可视化砷与绿锈硫酸盐的结合

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摘要

"Green rust" (GR), a redox-active Fe(Ⅱ)-Fe(Ⅲ) layered double hydroxide, is a potential environmentally relevant mineral substrate for arsenic (As) sequestration in reduced, subsurface environments. GR phases have high As uptake capacities at circum-neutral pH conditions, but the exact interaction mechanism between the GR phases and As species is still poorly understood. Here, we documented the bonding and interaction mechanisms between GR sulfate and As species [As(Ⅲ) and As(V)] under anoxic and circum-neutral pH conditions through scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray (EDX) spectroscopy and combined it with synchrotron-based X-ray total scattering, pair distribution function (PDF) analysis, and As K-edge X-ray absorption spectroscopy (XAS). Our highly spatially resolved STEM-EDX data revealed that the preferred adsorption sites of both As(Ⅲ) and As(V) are at GR crystal edges. Combining this data with differential PDF and XAS allowed us to conclude that As adsorption occurs primarily as bidentate binuclear (~2C) inner-sphere surface complexes. In the As(Ⅲ)-reacted GR sulfate, no secondary Fe-As phases were observed. However, authigenic parasymplesite (ferrous arsenate nanophase), exhibiting a threadlike morphology, formed in the As(V)-reacted GR sulfate and acts as an additional immobilization pathway for As(V) (~87% of immobilized As). We demonstrate that only by combining high-resolution STEM imaging and EDX mapping with the bulk (differential) PDF and extended X-ray absorption fine structure (EXAFS) data can one truly determine the de facto As binding nature on GR surfaces. More importantly, these new insights into As-GR interaction mechanisms highlight the impact of GR phases on As sequestration in anoxic subsurface environments.
机译：“绿锈”（GR）是一种具有氧化还原活性的Fe（Ⅱ）-Fe（Ⅲ）层状双氢氧化物，是在还原的地下环境中螯合砷的一种潜在的与环境有关的矿物底物。 GR相在环境中性pH条件下具有较高的As吸收能力，但对GR相与As物种之间确切的相互作用机理仍然知之甚少。在这里，我们通过扫描透射电子显微镜（STEM）结合能量色散X射线记录了在缺氧和环境中性pH条件下GR硫酸盐与As物种[As（Ⅲ）和As（V）]之间的键合和相互作用机理。 （EDX）光谱，并将其与基于同步加速器的X射线总散射，对分布函数（PDF）分析和As K边缘X射线吸收光谱（XAS）相结合。我们高度空间分辨的STEM-EDX数据表明，As（Ⅲ）和As（V）的首选吸附位均在GR晶体边缘。将该数据与差分PDF和XAS结合使用，可以得出结论：As吸附主要以双齿双核（〜2C）内球表面复合物的形式发生。在As（Ⅲ）反应的GR硫酸盐中，未观察到次生的Fe-As相。然而，在As（V）反应的GR硫酸盐中形成的自生准同位体（砷酸亚铁纳米相）呈线状形态，并作为As（V）（〜87％的固定化As）的附加固定化途径。我们证明只有将高分辨率STEM成像和EDX映射与大量（差分）PDF和扩展的X射线吸收精细结构（EXAFS）数据相结合，才能真正确定GR表面上的事实上的As结合性质。更重要的是，这些对As-GR相互作用机制的新见解突显了GR相对缺氧地下环境中As螯合的影响。

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  • 来源
    《Environmental Science & Technology》 |2020年第6期|3297-3305|共9页
  • 作者

    Jeffrey Paulo H. Perez; Helen M. Freeman; Andy P. Brown; Case M. van Genuchten; Knud Dideriksen; Mark Sari; Dominique J. Tobler; Liane G. Benning;

  • 作者单位

    GFZ German Research Center for Geosciences 14473 Potsdam Germany Department of Earth Sciences Freie Universitdt Berlin 12249 Berlin Germany;

    GFZ German Research Center for Geosciences 14473 Potsdam Germany School of Chemical and Process Engineering University of Leeds Leeds LS2 9JT United Kingdom;

    School of Chemical and Process Engineering University of Leeds Leeds LS2 9JT United Kingdom;

    Geological Survey of Denmark and Greenland (GEUS) 1350 Copenhagen Denmark Department of Earth Sciences Utrecht University Utrecht The Netherlands;

    Geological Survey of Denmark and Greenland (GEUS) 1350 Copenhagen Denmark Nano-Science Center Department of Chemistry University of Copenhagen 2100 Copenhagen Denmark;

    School of Chemical and Process Engineering University of Leeds Leeds LS2 9JT United Kingdom;

    Nano-Science Center Department of Chemistry University of Copenhagen 2100 Copenhagen Denmark;

    GFZ German Research Center for Geosciences 14473 Potsdam Germany Department of Earth Sciences Freie Universitdt Berlin 12249 Berlin Germany School of Earth and Environment University of Leeds Leeds LS2 9JT United Kingdom;

  • 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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