磁铁矿对废水中U(Ⅵ)的固定途径与机理

Approach and Mechanism of Immobilization of U(Ⅵ)by Magnetite From Aqueous Solution

综述了近年来磁铁矿对废水中U(Ⅵ)的固定途径与机理,总结了不同成因磁铁矿固定铀的机理差别及其主要的影响因素,深入梳理了磁铁矿的组成、结构和反应机理。磁铁矿对U(Ⅵ)的固定途径主要包括对六价铀酰的表面吸附、将U(Ⅵ)还原形成UO_(2)、在磁铁矿表面形成含U(Ⅳ)的内球表面配合物以及还原成U(Ⅴ)嵌入磁铁矿晶格结构等4种形式,不同成因磁铁矿、环境pH、磁铁矿化学计量、磁铁矿表面铀负荷以及碳酸盐和钙离子等都会影响U(Ⅵ)的最终固定形态。本研究结果对研究铀在水文地球化学中的迁移、固定铀的稳定性,以及评价铀深地质处置库的安全性具有重要意义。

The approach and mechanism of immobilization of U(Ⅵ)by magnetite from aqueous solution in recent years are reviewed,the paper also summarizes the differences in the mechanism of uranium fixation by magnetite of different genesis and its main influencing factors,thoroughly combs the composition,structure and reaction mechanism of magnetite,and studies the transformation of uranium in geochemistry and the stability of immobilized uranium.The immobilization pathways of U(Ⅵ)by magnetite mainly include surface adsorption of hexavalent uranyl,reduction of U(Ⅵ)to UO_(2),formation of inner-sphere complexes containing U(Ⅵ)on the surface of magnetite,as well as the reduced U(Ⅴ)is embedded in the crystal structure of magnetite.Magnetite of different genesis,environmental pH value,magnetite stoichiometry,uranium loading on the surface of magnetite,carbonate and calcium ions will affect the final fixed form of U(Ⅵ).The results of this study are of great significance for studying the migration of uranium in geochemistry,the stability of fixed uranium and evaluating the safety of uranium deep geological disposal repository.