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

摘要

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 on γ-FeOOH as neptunyl ion,with no observations of multinuclear surface complexes or surface precipitates.The Fourier trans-form(FT)magnitude of the EXAFS also shows an obvious peak feature at about 3 Å(1 Å=0.1 nm),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 composi-tions.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.%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3Å(1Å=0.1 nm )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。