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Atom Exchange between Aqueous Fe(Ⅱ) and Structural Fe in Clay Minerals

机译：粘土矿物中Fe（Ⅱ）与Fe的原子交换

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摘要

Due to their stability toward reductive dissolution, Fe-bearing clay minerals are viewed as a renewable source of Fe redox activity in diverse environments. Recent findings of interfacial electron transfer between aqueous Fe(Ⅱ) and structural Fe in clay minerals and electron conduction in octahedral sheets of nontronite, however, raise the question whether Fe interaction with clay minerals is more dynamic than previously thought. Here, we use an enriched isotope tracer approach to simultaneously trace Fe atom movement from the aqueous phase to the solid (~(57)Fe) and from the solid into the aqueous phase (~(56)Fe). Over 6 months, we observed a significant decrease in aqueous ~(57)Fe isotope fraction, with a fast initial decrease which slowed after 3 days and stabilized after about 50 days. For the aqueous ~(56)Fe isotope fraction, we observed a similar but opposite trend, indicating that Fe atom movement had occurred in both directions: from the aqueous phase into the solid and from the solid into aqueous phase. We calculated that 5-20% of structural Fe in clay minerals NAu-1, NAu-2, and SWa-1 exchanged with aqueous Fe(Ⅱ), which significantly exceeds the Fe atom layer exposed directly to solution. Calculations based on electron-hopping rates in nontronite suggest that the bulk conduction mechanism previously demonstrated for hematite and suggested as an explanation for the significant Fe atom exchange observed in goethite may be a plausible mechanism for Fe atom exchange in Fe-bearing clay minerals. Our finding of 5-20% Fe atom exchange in clay minerals indicates that we need to rethink how Fe mobility affects the macroscopic properties of Fe-bearing phyllosilicates and its role in Fe biogeochemical cycling, as well as its use in a variety of engineered applications, such as landfill liners and nuclear repositories.
机译：由于其对还原溶解的稳定性，因此含铁粘土矿物被视为在各种环境中可再生的铁氧化还原活性来源。然而，最近发现Fe（Ⅱ）与粘土矿物中的结构Fe之间的界面电子转移以及八面体的绿脱石层中电子的传导，提出了一个问题，即Fe与粘土矿物的相互作用是否比以前想象的更动态。在这里，我们使用富集同位素示踪法来同时跟踪Fe原子从水相到固相（〜（57）Fe）以及从固体到水相（〜（56）Fe）的运动。在6个月多的时间内，我们观察到〜（57）Fe同位素水溶液的含量显着下降，并且开始时快速下降，在3天后减慢并在约50天后稳定下来。对于〜（56）Fe同位素水溶液馏分，我们观察到了相似但相反的趋势，表明Fe原子的移动发生在两个方向：从水相到固体，从固体到水相。我们计算出粘土矿物NAu-1，NAu-2和SWa-1中的结构铁中有5-20％与含水的Fe（Ⅱ）交换，大大超过了直接暴露于溶液中的Fe原子层。基于绿脱石中电子跃变速率的计算表明，先前已证明赤铁矿具有整体传导机制，并暗示了针铁矿中大量Fe原子交换的解释可能是含Fe粘土矿物中Fe原子交换的合理机制。我们发现粘土矿物中5-20％的Fe原子交换表明，我们需要重新考虑Fe迁移率如何影响含Fe的层状硅酸盐的宏观性质及其在Fe生物地球化学循环中的作用，以及其在各种工程应用中的用途，例如垃圾填埋场衬里和核储存库。

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  • 来源
    《Environmental Science & Technology》 |2015年第5期|2786-2795|共10页
  • 作者

    Anke Neumann; Lingling Wu; Weiqiang Li; Brian L. Beard; Clark M. Johnson; Kevin M. Rosso; Andrew J. Frierdich; Michelle M. Scherer;

  • 作者单位

    Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, United States,Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom;

    Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, United States,Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada;

    Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, United States,School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu Province, 210046, China;

    Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, United States;

    Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, United States;

    Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States;

    Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, United States,Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, United States;

    Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, United States;

  • 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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