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首页> 外文期刊>Environmental Science & Technology >Reduction and Reoxidation of Humic Acid: Influence on Speciation of Cadmium and Silver
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Reduction and Reoxidation of Humic Acid: Influence on Speciation of Cadmium and Silver

机译：腐殖酸的还原和再氧化：对镉和银的形态的影响

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摘要

Naturally occurring variations of redox conditions are considered to affect the interactions between trace metals and humic substances in a 2-fold manner. First, additional proton binding sites of humic substances formed under reducing conditions may also act as binding sites for trace metals. Second, reduced humic substances may transfer electrons to redox-active trace metals. In this study, we investigated the influence of electrochemical reduction of a purified soil humic acid on the binding of two chalcophile metal cations of environmental concern, Cd~(2+) and Ag~+, with metal titrations conducted under monitored redox conditions. The binding of cadmium to reduced humic acid was slightly enhanced compared to humic acid reoxidized by O_2 and quantitatively in excellent agreement with the increase in binding sites formed upon reduction. Competitive experiments with calcium indicated that sulfur-containing sites played a minor role in cadmium binding, although sulfur K-edge XANES revealed that 36% of humic sulfur was in a reduced oxidation state. In all experiments with silver, the formation of Ag(0) was detected with transmission electron microscopy. Free Ag~+ activities under reducing conditions were controlled by Ag(0) formation rather than by binding to humic acid.
机译：氧化还原条件的自然发生变化被认为以2倍方式影响痕量金属与腐殖质之间的相互作用。首先，在还原条件下形成的腐殖质的其他质子结合位点也可以充当痕量金属的结合位点。其次，减少的腐殖质可将电子转移至氧化还原活性的痕量金属。在这项研究中，我们通过在监测的氧化还原条件下进行金属滴定，研究了电化学还原纯化的土壤腐殖酸对环境相关的两个亲硫金属阳离子Cd〜（2+）和Ag〜+的结合的影响。与被O_2再氧化的腐殖酸相比，镉与还原性腐殖酸的结合略有增强，并且与还原时形成的结合位点的增加在数量上非常吻合。钙的竞争性实验表明，尽管硫K边缘XANES揭示了36％的腐殖质硫处于还原态，但含硫位点在镉结合中的作用很小。在所有使用银的实验中，用透射电子显微镜检测到了Ag（0）的形成。还原条件下的游离Ag +活性是由Ag（0）的形成而不是与腐殖酸的结合来控制的。

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  • 来源
    《Environmental Science & Technology》 |2012年第16期|p.8808-8816|共9页
  • 作者

    Felix Maurer; Iso Christ; Martin Hoffmann; Ruben Kretzschmar;

  • 作者单位

    Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, CHN, 8092 Zurich, Switzerland;

    Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, CHN, 8092 Zurich, Switzerland;

    Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, CHN, 8092 Zurich, Switzerland;

    Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, CHN, 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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  • 正文语种 eng
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