Electrochemical Oxidation and Speciation of Lanthanides in Potassium Carbonate Solution
Electrochemical Oxidation and Speciation of Lanthanides in Potassium Carbonate Solution
复制标题
碳酸钾溶液中镧系元素的电化学氧化和形态形成
DOI：
10.1149/1945-7111/ac6704
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发表时间：
2022
影响因子：
3.9
通讯作者：
Shafer, Jenifer
中科院分区：
文献类型：
--
作者：
Tse, Poki;Bessen, Nathan P.;Galley, Shane S.;Bryan, Samuel A.;Lines, Amanda M.;Shafer, Jenifer
支持清洁能源目标的镧系元素需求不断增加，推动了开发更有效的方法来分离相邻镧系元素的需求。用于镧系元素分离的大多数方法不是非常选择性的，并且基于镧系元素离子半径的微小差异。浓缩的碳酸钾介质已经显示出能够将镨（Pr）和铽（Tb）氧化成其四价态的一些潜力，这最终能够基于氧化态的差异进行分离，但是关于该系统的化学性质知之甚少。这项工作完成了铈（Ce）氧化还原化学在浓缩的碳酸盐介质中的详细检查，以支持Pr和Tb氧化研究的发展。的Ce（III）/（IV）氧化还原电对的半波电位（E 1/2）的评估在各种溶液条件下和计算建模碳酸盐配位环境进行了讨论。循环伏安法显示较高的碳酸盐浓度和温度可以降低氧化Ce（III）所需的电位54 mV（3.5至5.5 M）和39 mV（10 C至70 C）。测时光度法表明Ce（III）和Ce（IV）碳酸盐配合物是化学稳定的和可逆的。计算模型表明，Ce（IV）配合物最可能的配位环境是Ce（CO 3）4（OH）5−，这比能量最低的Ce（III）配合物Ce（CO 3）4 5−的熵差。
Increasing lanthanide demand to support clean energy goals drives the need to develop more efficient approaches to separate adjacent lanthanides. Most approaches for lanthanide separations are not very selective and are based on small differences in lanthanide ionic radii. Concentrated potassium carbonate media has shown some potential to enable oxidation of praseodymium (Pr) and terbium (Tb) to their tetravalent states, which could ultimately enable a separation based on differences in oxidation states, but very little is known regarding the system's chemistry. This work completes a detailed examination of cerium (Ce) redox chemistry in concentrated carbonate media to support the development of Pr and Tb oxidation studies. The half-wave potential (E 1/2) of the Ce (III)/(IV) redox couple is evaluated under various solution conditions and computational modeling of carbonate coordination environments is discussed. Cyclic voltammetry shows higher carbonate concentrations and temperatures can lower the potential required to oxidize Ce (III) by 54 mV (3.5 to 5.5 M) and 39 mV (from 10 C to 70 C). Chronoabsorptometry shows Ce (III) and Ce (IV) carbonate complexes are chemically stable and reversible. Computational modelling suggests the most likely coordination environment for the Ce (IV) complex is Ce (CO 3) 4 (OH) 5− which is less entropically favorable than the lowest energy Ce (III) complex, Ce (CO 3) 4 5−.