Transferring from Eu³⁺ to Eu²⁺ in Eu₂O₃-LiCl-KCl molten salt: an optical and electrochemical investigation

Europium is an important element in the nuclear industry, which is usually applied in the high-temperature melt system. Therefore, due to relatively limited progress in understanding europium among all lanthanide elements, this study aims to disclose the important behavior of Eu³⁺ (Eu₂O₃) in the LiCl-KCl molten salt system employing optical and electrochemical strategies and to provide a theoretical basis for the subsequent electrolytic separation of Eu from other metals in nuclear waste. The optical behavior and electrochemical behavior of Eu₂O₃ in LiCl-KCl molten salt were tested by Raman, UV-vis diffuse reflectance spectra and CV, SWV, CP and other electrochemical methods. Through spectroscopic studies, it was found that Eu₂O₃ formed a new phase EuOCl in LiCl-KCl melt at 973 K. With the increase of Eu₂O₃ ratio, the band gap of products first increased and then decreased. Through electrochemical studies, it was found that Eu³⁺ underwent a single electron exchange process in LiCl-KCl melt, corresponding to the conversion between Eu(III) and Eu(II). The process was a quasi-reversible diffusion-controlled process. A series of electrochemical tests were carried out to determine the diffusion coefficient D of Eu (III) and Eu (II) as (1.94 ± 0.05) × 10⁻⁵ cm² s⁻¹ and (1.95 ± 0.05) × 10⁻⁵ cm² s⁻¹, respectively. This work reveals the electrolytic process of Eu³⁺ in molten system, which may influence on the spent fuel treatment.

铕（Europium）是核工业中的关键元素，常应用于高温熔盐体系。鉴于当前镧系元素中对铕的认知进展相对有限，本研究旨在通过光学与电化学表征手段，阐明三价铕离子（Eu³+，以三氧化二铕Eu₂O₃形式存在）在LiCl-KCl熔盐体系中的核心行为，并为后续从核废料中电解分离铕与其他金属提供理论支撑。
本研究采用拉曼光谱（Raman）、紫外-可见漫反射光谱（UV-vis diffuse reflectance spectra）以及循环伏安法（CV）、方波伏安法（SWV）、计时电位法（CP）等电化学方法，测试了三氧化二铕在LiCl-KCl熔盐中的光学行为与电化学行为。
光谱分析结果显示，三氧化二铕在973 K的LiCl-KCl熔盐中生成了新物相氯氧化铕（EuOCl）。随着三氧化二铕投料占比的提升，产物的禁带宽度先增大后减小。
电化学研究表明，三价铕离子在LiCl-KCl熔盐中经历单电子转移过程，对应三价铕与二价铕之间的相互转化，该过程为准可逆扩散控制过程。通过一系列电化学测试，测得三价铕与二价铕的扩散系数D分别为(1.94±0.05)×10⁻⁵ cm²·s⁻¹与(1.95±0.05)×10⁻⁵ cm²·s⁻¹。
本研究阐明了三价铕离子在熔盐体系中的电解过程，该成果或将对乏燃料后处理领域产生重要影响。

搜集汇总

背景与挑战

背景概述

该数据集通过光学和电化学方法研究了Eu2O3在LiCl-KCl熔盐中Eu3+向Eu2+的转移行为，发现形成新相EuOCl且带隙变化，并确定了Eu(III)和Eu(II)的扩散系数，为核废料中Eu的电解分离提供了理论基础。