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首页> 外文期刊>Environmental Science & Technology >Spectroscopic Evidence for Ternary Complex Formation between Arsenate and Ferric Iron Complexes of Humic Substances
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Spectroscopic Evidence for Ternary Complex Formation between Arsenate and Ferric Iron Complexes of Humic Substances

机译：腐殖质中砷和铁铁配合物三元配合物形成的光谱证据

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Formation of ternary complexes between arsenic (As) oxyanions and ferric iron (Fe) complexes of humic substances (HS) is often hypothesized to represent a major mechanism for As-HS interactions under oxic conditions. However, direct evidence for this potentially important binding mechanism is still lacking. To investigate the molecular-scale interaction between arsenate, As(V), and HS in the presence of Fe(Ⅲ), we reacted fulvic and humic acids with Fe(Ⅲ) (1 wt %) and equilibrated the Fe(Ⅲ)-HS complexes formed with As(V) at pH 7 (molar Fe/As ~10). The local (<5 A) coordination environments of As and Fe were subsequently studied by means of X-ray absorption spectroscopy. Our results show that 4.5- 12.5μmol As(V)/g HS (25-7096 of total As) was associated with Fe(Ⅲ). At least 70% of this As pool was bound to Fe(Ⅲ)-HS complexes via inner-sphere compilation. Results obtained from shell fits of As K-edge extended X-ray absorption fine structure (EXAFS) spectra were consistent with a monodentate binuclear (2C) and monodentate mononudear ('V) complex stabilized by H-bonds (Ra.-f? = 3 JO A). The analysis of Fe K-edge EXAFS spectra revealed that Fe in Fe(m)-HS complexes was predominantly present as ougomeric Fe(III) clusters at neutral pH. Shell-fit results complied with a structural motif in which three comer-sharing Fe(O,OH)6 octahedra linked by a single μ3-O bridge form a planar Fe trimer. In these complexes, the average Fe-C and Fe- Fe bond distances were 2.95 A and 3.47 A, respectively. Our study provides the first spectroscopic evidence for ternary complex formation between As(V) and Fe(Ⅲ)-HS complexes, suggesting that this binding mechanism is of fundamental importance for the cycling of oxyanions such as As(V) in organic-rich, one soils and sediments.
机译：通常认为，腐殖质（HS）的砷（As）氧阴离子和三价铁（Fe）配合物之间形成三元配合物是在有氧条件下As-HS相互作用的主要机理。但是，仍然缺少直接证据表明这种潜在的重要结合机制。为了研究在Fe（Ⅲ）存在下砷酸根，As（V）和HS之间的分子尺度相互作用，我们将黄腐酸和腐殖酸与Fe（Ⅲ）（1 wt％）反应并平衡Fe（Ⅲ）- HS复合物在pH 7时与As（V）形成（摩尔Fe / As约为10）。随后通过X射线吸收光谱研究了As和Fe的局部（<5 A）配位环境。结果表明，4.5-12.5μmolAs（V）/ g HS（总As的25-7096）与Fe（Ⅲ）有关。至少有70％的这种As池通过内球编译与Fe（Ⅲ）-HS配合物结合。从As K边缘扩展X射线吸收精细结构（EXAFS）光谱的壳拟合获得的结果与通过H键稳定的单齿双核（2C）和单齿单核（'V）络合物（Ra.-f？= 3 JO A）。 Fe K-edge EXAFS光谱分析表明，Fe（m）-HS络合物中的Fe在中性pH下主要以寡聚Fe（III）团簇的形式存在。壳拟合结果符合结构图案，其中通过单个μ3-O桥连接的三个共享角的Fe（O，OH）6八面体形成平面Fe三聚体。在这些络合物中，Fe-C和Fe-Fe的平均键距分别为2.95 A和3.47A。我们的研究为As（V）和Fe（Ⅲ）-HS配合物之间的三元配合物形成提供了第一个光谱学证据，表明这种结合机制对于富含有机物的含氧阴离子如As（V）的循环至关重要。一种土壤和沉积物。

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  • 来源
    《Environmental Science & Technology》 |2011年第22期|p.9550-9557|共8页
  • 作者

    Christian Mikutta; Ruben Kretzschmar;

  • 作者单位

    Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, 8092 Zurich, Switzerland;

    Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, 8092 Zurich, Switzerland;

  • 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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