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磺酸型阳离子树脂的元素分配行为及高精度同位素分析应用

Elemental Distribution Behavior of Sulfonic Acid Cation-Exchange Resins and Applications to High-precision Isotope Analysis

  • 摘要: 不同元素在离子交换树脂的分配系数是元素纯化和分离的基础,不同酸中各元素分配系数差异可用于设计高效的元素提纯流程,从而被广泛应用于现代高精度同位素分析。本文以AG®50W-X8阳离子树脂为研究对象,以分配系数(Kd)作为量化指标,通过系统实验研究不同元素在该树脂中的分配行为。在前人研究基础上,本实验增加了元素数量和酸的种类,涵盖了金属、类金属、非金属和稀土元素。结果表明:在盐酸和硝酸介质中,几乎所有元素的Kd都与酸度呈负相关,当酸度达到6mol/L时,除Th和Ca以外的所有元素都会被酸洗脱。稀土元素(REEs)和高场强元素在0.1~0.5mol/L稀硝酸和稀盐酸中强烈吸附在树脂上;而一些过渡金属、类金属和非金属元素(如Mo、W、Re、Ir、Sb、Ge、As、Se、Te等)在酸溶液中会形成含氧阴离子,不与阳离子树脂发生吸附。Al、Fe、Se、Pd、Cd、In等元素在盐酸中易与氯离子形成配位化合物或离子团,导致这些离子在盐酸中的分配系数显著降低。在硝酸和盐酸与氢氟酸的混合酸中,除稀土元素外,绝大部分元素随酸度增加Kd迅速降低。稀土元素在盐酸-氢氟酸混合介质中,随着盐酸的浓度增加(从0.1mol/L盐酸-0.2mol/L氢氟酸至6mol/L盐酸-0.2mol/L氢氟酸),稀土元素分配系数(KdREE)具有先增加后降低的趋势。氢氟酸的加入可显著降低Be、Al、Sc、Fe、Sn、Th、U、Ti、Zr、Hf等元素在稀盐酸和稀硝酸中的分配系数,使这些元素几乎不与树脂发生吸附。本研究揭示了不同酸介质中各类元素在阳离子交换树脂上的分配行为存在差异,尤其是氢氟酸的加入可显著改变高场强元素、部分过渡金属和稀土元素的分配系数,为应用该树脂开发和优化适用于高精度金属稳定同位素分析的元素提纯流程(如Li、Mg、K、Sr、Ce、U等)提供了数据支撑,并可有效地减少后续实验设计的工作量。

     

    Abstract: The distribution coefficient (Kd) of elements in ion exchange resin is the basis of element purification and separation, which is the premise for high-precision isotope analysis. However, systematic comparison of the Kd in different types of acid is lacking, which has hindered the development of efficient separation procedures for emerging isotope system. In this research, the Kd of 60 elements in AG®50W-X8 cationic resin with different concentrations and types of acid was studied. Our results show that, in acid solutions, the Kd of almost all elements is negatively related to acidity. Compared to nitric acid, a significant decrease in the Kd for Al, Fe, Se, Pd, Cd, and In is observed in hydrochloric acid. The addition of hydrofluoric acid can significantly reduce the Kd of Be, Al, Sc, Fe, Sn, Th, U, Ti, Zr, and Hf in dilute hydrochloric and nitric acid, so that they can be quantitively eluted from the resin. In the mixed hydrofluoric acid solutions, KdREE shows an initial increasing and then decreasing trend as the concentration of HCl increases. The present study provides data support for the development and optimization of element purification processes that are suitable for high-precision metal stable isotope analysis. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202309260154.

     

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