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Iron Atom Exchange between Hematite and Aqueous Fe(Ⅱ)

机译：赤铁矿与Fe（Ⅱ）之间的铁原子交换

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摘要

Aqueous Fe(Ⅱ) has been shown to exchange with structural Fe(Ⅲ) in goethite without any significant phase transformation. It remains unclear, however, whether aqueous Fe(Ⅱ) undergoes similar exchange reactions with structural Fe(Ⅲ) in hematite, a ubiquitous iron oxide mineral. Here, we use an enriched ~(57)Fe tracer to show that aqueous Fe(Ⅱ) exchanges with structural Fe(Ⅲ) in hematite at room temperature, and that the amount of exchange is influenced by particle size, pH, and Fe(Ⅱ) concentration. Reaction of 80 nm-hematite (27 m~2 g~(-1)) with aqueous Fe(Ⅱ) at pH 7.0 for 30 days results in ～5% of its structural Fe(Ⅲ) atoms exchanging with Fe(Ⅱ) in solution, which equates to about one surface iron layer. Smaller, 50 nm-hematite particles (54 m~2 g~(-1)) undergo about 25% exchange (～3X surface iron) with aqueous Fe(Ⅱ), demonstrating that structural Fe(Ⅲ) in hematite is accessible to the fluid in the presence of Fe(Ⅱ). The extent of exchange in hematite increases with pH up to 7.5 and then begins to decrease as the pH progresses to 8.0, likely due to surface site saturation by sorbed Fe(Ⅱ). Similarly, when we vary the initial amount of added Fe(Ⅱ), we observe decreasing amounts of exchange when aqueous Fe(Ⅱ) is increased beyond surface saturation. This work shows that Fe(Ⅱ) can catalyze iron atom exchange between bulk hematite and aqueous Fe(Ⅱ), despite hematite being the most thermodynamically stable iron oxide.
机译：Fe（Ⅱ）在针铁矿中与结构Fe（Ⅲ）交换而没有任何明显的相变。然而，尚不清楚在泛铁氧化物矿物赤铁矿中，Fe（Ⅱ）水溶液是否与结构Fe（Ⅲ）发生类似的交换反应。在这里，我们使用了丰富的〜（57）Fe示踪剂，表明室温下赤铁矿中的Fe（Ⅱ）水溶液与结构Fe（Ⅲ）交换，并且交换量受粒度，pH和Fe（ Ⅱ）集中。 80 nm赤铁矿（27 m〜2 g〜（-1））与Fe（Ⅱ）水溶液在pH 7.0下反应30天，导致〜5％的结构Fe（Ⅲ）原子与Fe（Ⅱ）交换。溶液，相当于一个表面铁层。较小的50 nm赤铁矿颗粒（54 m〜2 g〜（-1））与Fe（Ⅱ）水溶液进行约25％的交换（约3X表面铁），表明赤铁矿中的结构性Fe（Ⅲ）易于进入Fe（Ⅱ）存在下的流体。当pH达到7.5时，赤铁矿的交换程度增加，然后随着pH值达到8.0而开始下降，这可能是由于吸附的Fe（Ⅱ）使表面位点饱和所致。同样，当我们改变最初添加的Fe（Ⅱ）的量时，我们观察到当Fe（Ⅱ）的水溶液增加到超过表面饱和度时交换量减少。这项工作表明，尽管赤铁矿是热力学上最稳定的氧化铁，但Fe（Ⅱ）可以催化块状赤铁矿与含水Fe（Ⅱ）之间的铁原子交换。

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  • 来源
    《Environmental Science & Technology》 |2015年第14期|8479-8486|共8页
  • 作者

    Andrew J. Frierdich; Maria Helgeson; Chengshuai Liu; Chongmin Wang; Kevin M. Rosso; Michelle M. Scherer;

  • 作者单位

    Department of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa 52242, United States,Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, United States,School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, Australia;

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

    Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650, P. R. China,State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;

    Pacific Northwest National Laboratory, Richland, Washington 99352, United States;

    Pacific Northwest National Laboratory, Richland, Washington 99352, United States;

    Department of Civil and Environmental Engineering, 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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