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首页> 外文期刊>Environmental Science & Technology >Spectroscopic Investigation of Cr(Ⅲ)- and Cr(Ⅵ)-Treated Nanoscale Zerovalent Iron
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Spectroscopic Investigation of Cr(Ⅲ)- and Cr(Ⅵ)-Treated Nanoscale Zerovalent Iron

机译：Cr（Ⅲ）-和Cr（Ⅵ）-处理的纳米零价铁的光谱研究

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The reaction of hexavalent chromium (Cr(Ⅵ)) with zerovalent iron (Fe~0) during soil and groundwater remediation is an important environmental process. This study used several techniques including X-ray photoelectron spectros-copy (XPS) and X-ray absorption spectroscopy to investigate nanometer scale Fe~0 particles (nano Fe~0) treated with Cr(Ⅲ) and Cr(Ⅵ). X-ray diffraction and XPS analyses of oxidized nano Fe~0 showed the crystalline Fe(Ⅲ) phase is composed of lepidocrocite (γ-FeOOH). Results of XPS Cr 2p data and Cr K-edge X-ray absorption near edge spectroscopy (XANES) provided evidence that Cr(Ⅵ) was entirely reduced to Cr(Ⅲ) by nano Fe~0 with no residual Cr(Ⅵ) after reaction. In addition, XPS and XANES results of Cr(Ⅲ) precipitated as Cr(OH)_3 in the presence of corroding nano Fe~0 were nearly identical to the Cr(Ⅵ)-nano Fe~0 reaction product. Detailed analysis of XPS 0 1s line spectra revealed that both Cr(Ⅲ)- and Cr(Ⅵ)-treated nano Fe~0 yielded a predominantly hydroxylated Cr(OH)_3 and/or a mixed phase Cr_xFe_(1-x)(OH)_3 product. The structure of the Cr(Ⅲ)- and Cr(Ⅵ)-treated nano Fe~0 determined using extended X-ray absorption fine structure spectroscopy (EXAFS) revealed octahedral Cr(Ⅲ) with Cr-0 interatomic distances between 1.97 and 1.98 A for both Cr(Ⅲ) and Cr-(Ⅵ) treatments and a pronounced Cr—Cr second interatomic shell at 3.01 A. Our results suggest that the reaction product of Cr(Ⅵ)-treated nano Fe~0 is either a poorly ordered Cr(OH)_3 precipitate or possibly a mixed phase Cr_xFe_(1-x)(OH)_3 product, both of which are highly insoluble under environmental conditions.
机译：土壤和地下水修复过程中六价铬（Cr（Ⅵ））与零价铁（Fe〜0）的反应是重要的环境过程。本研究使用X射线光电子能谱（XPS）和X射线吸收光谱等技术研究了用Cr（Ⅲ）和Cr（Ⅵ）处理的纳米级Fe〜0粒子（纳米Fe〜0）。氧化后的纳米Fe〜0的X射线衍射和XPS分析表明，结晶的Fe（Ⅲ）相由纤铁矿（γ-FeOOH）组成。 XPS Cr 2p数据和Cr K边缘X射线吸收近边缘光谱（XANES）的结果提供了证据，表明纳米Fe〜0将Cr（Ⅵ）完全还原为Cr（Ⅲ），反应后没有残留的Cr（Ⅵ）。 。另外，在腐蚀的纳米Fe〜0存在下，Cr（Ⅲ）以C​​r（OH）_3的形式析出的XPS和XANES结果与Cr（Ⅵ）-纳米Fe〜0反应产物几乎相同。 XPS 0 1s线谱的详细分析表明，Cr（Ⅲ）和Cr（Ⅵ）处理的纳米Fe〜0均产生主要为羟基化的Cr（OH）_3和/或混合相Cr_xFe_（1-x）（OH） ）_3产品。用扩展X射线吸收精细结构光谱法（EXAFS）测定的Cr（Ⅲ）和Cr（Ⅵ）处理的纳米Fe〜0的结构表明八面体Cr（Ⅲ）的Cr-0原子间距在1.97和1.98 A之间。 Cr（Ⅲ）和Cr-（Ⅵ）处理的结果以及在3.01 A时有明显的Cr-Cr第二原子间壳层。我们的结果表明，Cr（Ⅵ）处理的纳米Fe〜0的反应产物要么是有序的Cr （OH）_3沉淀或可能是混合相Cr_xFe_（1-x）（OH）_3产物，两者在环境条件下均高度不溶。

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