Adsorption of Tetrathiomolybdate to Iron Sulfides and Its Impact on Iron Sulfide Transformations-猫眼课题宝

DOI：

10.1021/acsearthspacechem.0c00176

发表时间：

2020-11

期刊：

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其他

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作者：

Nathan Miller;M. Dougherty;Ruochen Du;T. Sauers;Candice Yan;J. Pines;Kate L. Meyers;Y. Dang;Emily Nagle;Ziqin Ni;T. Pungsrisai;Maxwell T. Wetherington;Trent P. Vorlicek;Katherine E. Plass;J. Morford

海洋沉积物中的钼（Mo）通过与黄铁矿的共生关系，被用作古代用指标，为过去海洋富氧和硫化物环境提供证据。在这里，我们研究的吸附钼的黄铁矿前体mackinawite和硫砷铜矿和评估的鲁棒性，这种协会在硫化铁相变。四硫代钼酸盐（MoS 42-）的吸附实验进行了使用mackinawite和云英岩，其特征在于使用粉末X射线衍射和拉曼光谱。四硫代钼酸盐的吸附mackinawite和主要的云英岩混合物是相似的。两者在吸附后对矿物相几乎没有变化。相对于以前发表的数据黄铁矿，有更大量的钼吸附和不同的吸附模式。还通过一种替代方法合成了mackinawite/greigite混合物，该方法更接近地模拟环境条件，具有短暂的原位老化以形成硫化铁的初始相，可能是高度无序的mackinawite，并且几乎立即添加MoS 42-。X射线光电子能谱结果支持四硫代钼酸盐的吸附及其伴随的还原钼（IV）。Mo-吸附mackinawite/云英岩混合物通过加热转化成云英岩/黄铁矿混合物，同时监测Mo释放到水相。在这里，吸附在固相上的钼促进转化的mackinawite到黄铁矿加热后，没有成岩损失的钼的水相。这些结果支持早期捕获的MoS 42-不太稳定的形式的硫化铁，可以忽略不计的成岩损失在随后的转换。这项工作继续指出Mo（VI）是自然缺氧环境中FeS到FeS 2的合理氧化剂。

Molybdenum (Mo) in marine sediments has been used as a paleoproxy to provide evidence for past oceanic euxinic and sulfidic conditions through its association with pyrite. Here, we examine the adsorption of Mo to the pyrite precursors mackinawite and greigite and assess the robustness of this association during iron sulfide phase transformations. Tetrathiomolybdate (MoS42–) adsorption experiments were done using mackinawite and greigite that had been characterized using powder X-ray diffraction and Raman spectroscopy. Adsorption of tetrathiomolybdate to mackinawite and to a primarily greigite mixture was similar. Both showed little change to the mineral phase upon adsorption. Relative to previously published data on pyrite, there was a much greater amount of Mo adsorption and a different mode of adsorption. A mackinawite/greigite mixture was also synthesized through an alternative method that more closely mimicked environmental conditions with a brief in situ aging to form an initial phase of iron sulfide, likely highly disordered mackinawite, and the near-immediate addition of MoS42–. X-ray photoelectron spectroscopy results support the adsorption of tetrathiomolybdate and its concomitant reduction to Mo(IV). The Mo-adsorbed mackinawite/greigite mixture was transformed through heating into a greigite/pyrite mixture while monitoring Mo release to the aqueous phase. Here, the sorption of Mo on the solid phase promoted the transformation of mackinawite into pyrite upon heating without diagenetic loss of Mo to the aqueous phase. These results support the early capture of MoS42–to less-stable forms of iron sulfide with negligible diagenetic loss during subsequent transformation. This work continues to point to Mo(VI) as a plausible oxidant of FeS to FeS2within natural euxinic settings.

Adsorption of Tetrathiomolybdate to Iron Sulfides and Its Impact on Iron Sulfide Transformations

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