Np(Ⅴ)吸附于纤铁矿/水界面的扩展X射线吸收精细结构(EXAFS)分析

Neptunium(Ⅴ) Adsorption to γ-FeOOH/Water Interface:EXAFS Analysis

本工作采用原位扩展X射线吸收精细结构(EXAFS)能谱首次揭示了Np(Ⅴ)吸附于合成纤铁矿(γ-FeOOH)表面的化学形态。Np LⅢ边EXAFS分析结果显示Np(Ⅴ)以五价镎酰离子吸附于γ-FeOOH,未发现多核络合物与表面沉淀。傅里叶转化结果在约3(1=0.1nm)附近的能峰可归于Np-Fe配位层,证明了Np(Ⅴ)-γ-FeOOH形成了内层吸附的单一形态表面络合物。所得分析结果与Np(Ⅴ)在相似构成的含铁矿物上的吸附形态结果进行了比较,进一步确认了Np-Fe、Np-O等关键配位层的存在。然而,还需要更多设计良好的EXAFS实验来确认是否存在Np-C配位层,以确认纤铁矿界面是否存在Np碳酸根表面络合物。

This work apply in situ extended X-ray absorption fine structure（EXAFS）to reveal sorption speciation of Np（Ⅴ）on synthetic lepidocrocite（γ-FeOOH）.Np LⅢ-edge EXAFS analysis shows that Np（Ⅴ）is absorbed onγ-FeOOH as neptunyl ion,with no observations of multinuclear surface complexes or surface precipitates.The Fourier transform（FT）magnitude of the EXAFS also shows an obvious peak feature at about 3（1=0.1nm）,that can be attributed to a Np-Fe scattering path,consistent with the formation of an inner sphere Np（Ⅴ）-lepidocrocite surface complex.The EXAFS FT results were compared between Np（Ⅴ）speciation on difference iron mineral phases with similar compositions.However,it remains a question whether or not a Np-C coordination exists,indicating the possible presence of Np（Ⅴ）/carbonate species on the lepidocrocite surface.Additional studies are needed,particularly well-designed EXAFS studies,to answer this question and verify the identity of the surface complex.