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Recrystallization of Manganite (γ-MnOOH) and Implications for Trace Element Cycling

机译：锰（γ-MnOOH）的再结晶及其对痕量元素循环的意义

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The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II)_(aq)) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with Manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II)_(aq) under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a ~(62)Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the Manganite crystal structure during reactions in 1 mM Mn(II)_(aq) and in Mn(II)-free solutions. XAS spectra show that Ni is initially sorbed on the Manganite mineral surface and is progressively incorporated into the mineral structure over time (13% after 51 days) even in the absence of dissolved Mn(II). The amount of Ni incorporation significantly increases to about 40% over a period of 51 days when Mn(II)_(aq) is present in solution. Similarly, Mn(II)_(aq) promotes Ni exchange between Ni-substituted Manganite and dissolved Ni(II), with around 30% of Ni exchanged at pH 7.5 over the duration of the experiment. No new mineral phases are detected following recrystallization as determined by X-ray diffraction and XAS. Our results reveal that Mn(II)-catalyzed mineral recrystallization partitions Ni between Mn oxides and aqueous fluids and can therefore affect Ni speciation and mobility in the environment.
机译：在（生物）地球化学Mn氧化还原循环过程中，Mn（II）（Mn（II）_（aq））水溶液催化Mn（III，IV）氧化物的重结晶。人们对这种再结晶过程中与锰氧化物（例如镍）有关的痕量金属是如何循环的了解甚少。在这里，我们使用X射线吸收光谱法（XAS）在可变pH条件下，在存在或不存在Mn（II）_（aq）的情况下，检查与锰矿（γ-Mn（III）OOH）悬浮液相关的Ni的形态（ pH 5.5和7.5）。在第二组实验中，我们使用〜（62）Ni同位素示踪剂来量化在1 mM Mn（II）_（aq）和Mn中反应过程中与掺入锰矿晶体结构中的Ni交换的溶解Ni的量。 （II）无解决方案。 XAS光谱表明，即使不存在溶解的Mn（II），Ni也会最初吸附在锰矿矿物表面上，并随时间（51天后为13％）逐渐掺入矿物结构中。当溶液中存在Mn（II）_（aq）时，在51天内Ni的掺入量显着增加至约40％。同样，Mn（II）_（aq）促进Ni取代的锰矿和溶解的Ni（II）之间的Ni交换，在整个实验过程中，约有30％的Ni在pH 7.5时交换。通过X射线衍射和XAS测定，重结晶后未检测到新的矿物相。我们的结果表明，Mn（II）催化的矿物重结晶将Ni分配在Mn氧化物和水性流体之间，因此可以影响Ni的形态和在环境中的迁移率。

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  • 来源
    《Environmental Science & Technology》 |2018年第3期|1311-1319|共9页
  • 作者

    Tobias Hens; Joël Brugger; Susan A. Cumberland; Barbara Etschmann; Andrew J. Frierdich;

  • 作者单位

    School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria 3800, Australia;

    School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria 3800, Australia;

    School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria 3800, Australia,Australian Synchrotron, Clayton, Victoria 3168, Australia;

    School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria 3800, Australia;

    School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria 3800, Australia;

  • 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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