Eddy Madeleine A, Picayo Gabriela A, Jensen Mark P
Chemistry Department, Colorado School of Mines, Golden, Colorado 80401, United States.
Chemistry Department and Nuclear Science and Engineering Program, Colorado School of Mines, Golden, Colorado 80401, United States.
ACS Omega. 2022 Apr 19;7(17):15005-15015. doi: 10.1021/acsomega.2c00759. eCollection 2022 May 3.
The actinide lanthanide separation (ALSEP) process is a modern solvent extraction approach used for the separation of the minor actinides americium and curium from the lanthanide fission products for transmutation, a process that can significantly reduce the long-term radioactivity and heat loading of nuclear waste. This process, inspired by existing chemistry, uses the aminopolycarboxylate -(2-hydroxyethyl)ethylenediamine-,,-triacetic acid (HEDTA) to selectively separate the actinides by stripping them from the organic phase while leaving the lanthanides behind. HEDTA is used in this separation as it has been shown to exhibit faster extraction kinetics than other aminopolycarboxylates, but its lower coordination number can allow for the formation of higher order complexes with the typically 8- to 9-coordinate f-elements. ALSEP uses a carboxylic acid buffer in the aqueous phase to control the pH of the system during metal stripping, and this buffer has the ability to complex actinide(III) and lanthanide(III) ions. The presence of a previously uncharacterized ternary lanthanide-HEDTA-citrate complex was detected during single-phase spectroscopy experiments. A combination of partitioning experiments and spectrophotometric titrations led to the identification of a 1:1:1 complex containing a partially protonated citrate ligand and determination of the stability constant of its neodymium complex.
锕系元素 - 镧系元素分离（ALSEP）工艺是一种现代溶剂萃取方法，用于从镧系裂变产物中分离次锕系元素镅和锔以进行嬗变，该过程可显著降低核废料的长期放射性和热负荷。此工艺受现有化学原理启发，使用氨基多羧酸盐 -（2 - 羟乙基）乙二胺 - N,N,N' - 三乙酸（HEDTA），通过将锕系元素从有机相中反萃出来而选择性地分离它们，同时使镧系元素留在有机相中。HEDTA用于这种分离是因为已证明它比其他氨基多羧酸盐具有更快的萃取动力学，但其较低的配位数可以允许与通常8至9配位的f元素形成高阶配合物。ALSEP在水相中使用羧酸缓冲剂来控制金属反萃过程中系统的pH值，并且这种缓冲剂能够络合锕系元素（III）和镧系元素（III）离子。在单相光谱实验中检测到一种先前未表征的三元镧系元素 - HEDTA - 柠檬酸盐配合物。分配实验和分光光度滴定相结合，鉴定出一种含有部分质子化柠檬酸盐配体的1:1:1配合物，并测定了其钕配合物的稳定常数。
