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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >Aqueous Cr(VI) reduction by pyrite: Speciation and characterisation of the solid phases by X-ray photoelectron, Raman and X-ray absorption spectroscopies
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Aqueous Cr(VI) reduction by pyrite: Speciation and characterisation of the solid phases by X-ray photoelectron, Raman and X-ray absorption spectroscopies

机译：黄铁矿还原Cr（VI）水溶液：X射线光电子，拉曼光谱和X射线吸收光谱法对固相的形态和表征

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Optical microscopy, confocal Raman micro-spectrometry, X-ray photoelectron micro-spectroscopy (XPS) and synchrotron based micro-X-ray fluorescence (XFY), micro-X-ray absorption near edge spectroscopy (XANES) and micro-extended X-ray absorption fine structure (EXAFS) were used to investigate the reduction of aqueous Cr(VI) by pyrite. Special emphasis was placed on the characterisation of the solid phase formed during the reaction process. Cr(III) and Fe(III) species were identified by XPS analyses in addition to non-oxidised pyrite. Optical microscopy images and the corresponding Raman spectra reveal a strong heterogeneity of the samples with three different types of zones. (i) Reflective areas with E, and A, Raman wavenumbers relative to non-oxidised pyrite are the most frequently observed. (ii) Orange areas that display a drift of the E. and A, pyrite vibration modes of -3 and -6 cm(-1) respectively. Such areas are only observed in the presence of Cr(VI) but are not specifically due to this oxidant. (iii) Bluish areas with vibration modes relative to a corundum-like structure that can be assigned to a solid solution Fe2-x,CrxO3, x varying between 0.2 and 1.5. The heterogeneity in the spatial distribution of chromium observed by optical microscopy and associated Raman microspectroscopy is confirmed by mu-XRF. In agreement with both solution and XPS analyses, these spectroscopies clearly confirm that chromium is in the trivalent state, XANES spectra in the iron K-edge pre-edge region obtained in rich chromium areas reveal the presence of ferric ion thus revealing a systematic association between Cr(III) and Fe(III). In agreement with Raman analyses, Cr K-edge EXAFS can be interpreted as corresponding to Cr atoms involved in a substituted-type hematite structure Fe2-xCrxO3. (c) 2006 Elsevier Ltd. All rights reserved.
机译：光学显微镜，共聚焦拉曼光谱，X射线光电子显微光谱（XPS）和基于同步加速器的微型X射线荧光（XFY），近边缘光谱的微型X射线吸收（XANES）以及微扩展X射线射线吸收精细结构（EXAFS）用于研究黄铁矿对Cr（VI）的还原作用。特别强调反应过程中形成的固相的表征。除非氧化的黄铁矿外，还通过XPS分析鉴定了Cr（III）和Fe（III）物种。光学显微镜图像和相应的拉曼光谱显示具有三种不同类型区域的样品具有很强的异质性。 （i）最常见的反射区域是E和A，相对于未氧化的黄铁矿的拉曼波数。 （ii）橙色区域显示E.和A的漂移，黄铁矿振动模式分别为-3和-6 cm（-1）。仅在Cr（VI）存在的情况下才能观察到此类区域，但不是由于该氧化剂而引起的。 （iii）相对于刚玉状结构具有振动模式的模糊区域，可以分配给固溶体Fe2-x，CrxO3，x在0.2和1.5之间变化。通过mu-XRF证实了通过光学显微镜和相关的拉曼光谱法观察到的铬空间分布的异质性。与溶液和XPS分析相一致，这些光谱学清楚地证实了铬处于三价态，在富铬区域获得的铁K边缘预边缘区域中的XANES光谱揭示了三价铁离子的存在，从而揭示了铁离子之间的系统关联。 Cr（III）和Fe（III）。与拉曼分析一致，Cr K-edge EXAFS可以解释为对应于取代型赤铁矿结构Fe2-xCrxO3中涉及的Cr原子。 （c）2006 Elsevier Ltd.保留所有权利。

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