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首页> 外文期刊>Environmental Science & Technology >Selenite Reduction by Mackinawite, Magnetite and Siderite: XAS Characterization of Nanosized Redox Products
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Selenite Reduction by Mackinawite, Magnetite and Siderite: XAS Characterization of Nanosized Redox Products

机译：Mackinawite，磁铁矿和菱铁矿还原亚硒酸盐：纳米氧化还原产物的XAS表征

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Suboxic soils and sediments often contain the Fe(Ⅱ)-bearing minerals mackinawite (FeS), siderite (FeCO_3) or magnetite (Fe_3O_4), which should be able to reduce aqueous selenite, thereby forming solids of low solubility. While the reduction of selenate or selenite to Se(O) by green rust, pyrite and by Fe~(2+) sorbed to montmorillonite is a slow (weeks), kinetically limited redox reaction as demonstrated earlier, we show here that selenite is rapidly reduced within one day by nanoparticulate mackinawite and magnetite, while only one third of selenite is reduced by micrometer-sized siderite. Depending on Fe(Ⅱ)-bearing phase and pH, we observed four different reaction products, red and gray elemental Se, and two iron selenides with structures similar to Fe_7Se_8 and FeSe. The thermodynamically most stable iron selenide, ferroselite (FeSe_2), was not observed. The local structures of the reaction products suggest formation of nanoscale clusters, which may be prone to colloid-facilitated transport, and may have a higher than expected solubility.
机译：含碳的土壤和沉积物通常包含含Fe（Ⅱ）的矿物质马基钠铁矿（FeS），菱铁矿（FeCO_3）或磁铁矿（Fe_3O_4），它们应能够还原含水亚硒酸盐，从而形成低溶解度的固体。尽管绿锈，黄铁矿和吸附到蒙脱石上的Fe〜（2+）将硒酸盐或亚硒酸盐还原为Se（O）的过程很慢（几周），但动力学上有限，氧化还原反应如前所述，但在这里我们证明了亚硒酸盐迅速在一天之内被纳米颗粒的麦基磁铁矿和磁铁矿所还原，而亚硒酸盐仅被微米尺寸的菱铁矿所还原。根据含Fe（Ⅱ）的相和pH，我们观察到四种不同的反应产物，红色和灰色元素硒，以及两种结构类似于Fe_7Se_8和FeSe的硒化铁。没有观察到热力学上最稳定的亚硒酸铁铁矿（FeSe_2）。反应产物的局部结构表明形成纳米级簇，其可能易于胶体促进的运输，并且可能具有高于预期的溶解度。

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