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首页> 外文期刊>Geosciences >Neptunium Reactivity During Co-Precipitation and Oxidation of Fe(II)/Fe(III) (Oxyhydr)oxides
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Neptunium Reactivity During Co-Precipitation and Oxidation of Fe(II)/Fe(III) (Oxyhydr)oxides

机译：Fe（II）/ Fe（III）（羟基）氧化物共沉淀和氧化过程中的反应性

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Fe(II) bearing iron (oxyhydr)oxides were directly co-precipitated with Np(V)O 2 + under anaerobic conditions to form Np doped magnetite and green rust. These environmentally relevant mineral phases were then characterised using geochemical and spectroscopic analyses. The Np doped mineral phases were then oxidised in air over 224 days with solution chemistry and end-point oxidation solid samples collected for further characterisation. Analysis using chemical extractions and X-ray absorption spectroscopy (XAS) techniques confirmed that Np(V) was initially reduced to Np(IV) during co-precipitation of both magnetite and green rust. Extended X-Ray Absorption Fine Structure (EXAFS) modelling suggested the Np(IV) formed a bidentate binuclear sorption complex to both minerals. Furthermore, following oxidation in air over several months, the sorbed Np(IV) was partially oxidised to Np(V), but very little remobilisation to solution occurred during oxidation. Here, linear combination fitting of the X-Ray Absorption Near Edge Structure (XANES) for the end-point oxidation samples for both mineral phases suggested approximately 50% oxidation to Np(V) had occurred over 7 months of oxidation in air. Both the reduction of Np(V) to Np(IV) and inner sphere sorption in association with iron (oxyhydr)oxides, and the strong retention of Np(IV) and Np(V) species with these phases under robust oxidation conditions, have important implications in understanding the mobility of neptunium in a range of engineered and natural environments.
机译：在厌氧条件下，含Fe（II）的铁（羟基）氧化物与Np（V）O 2 +直接共沉淀，形成Np掺杂磁铁矿和绿锈。然后使用地球化学和光谱分析对这些与环境有关的矿物相进行表征。然后用溶液化学方法在空气中将Np掺杂的矿物相氧化224天，并收集端点氧化的固体样品用于进一步表征。使用化学提取和X射线吸收光谱（XAS）技术进行的分析证实，在磁铁矿和生铁锈的共沉淀过程中，Np（V）最初被还原为Np（IV）。扩展的X射线吸收精细结构（EXAFS）建模表明Np（IV）对两种矿物形成了双齿双核吸附复合物。此外，在空气中氧化数月后，吸附的Np（IV）被部分氧化为Np（V），但在氧化过程中很少发生固溶。在这里，两种矿物相的终点氧化样品的X射线吸收近边缘结构（XANES）的线性组合拟合表明，在空气中氧化7个月后，大约有50％的氧化成Np（V）。 Np（V）还原为Np（IV）以及与铁（羟基氧化物）氧化物相关的内球吸附，以及在强力氧化条件下这些相对Np（IV）和Np（V）的强烈保留，都具有对于理解n在一系列工程和自然环境中的迁移性具有重要意义。

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