Towards understanding the correlation between UO22+ extraction and substitute groups in 2,9-diamide-1,10-phenanthroline
作者:Xinrui Zhang、Liyong Yuan、Zhifang Chai、Weiqun Shi
DOI:10.1007/s11426-018-9227-1
日期:2018.10
2,9-Diamide-1,10-phenanthroline (DAPhen) ligands represent a new family of tetradentate extractants given their strong affinity to actinides and the CHON principle. Among this family, N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), initially reported by us, exhibits excellent selectivity towards actinides (U, Th, Am, Pu) over lanthanides and thus can be potentially applied in the group actinide extraction (GANEX) process for the group separation of actinides. In this article, by tailoring the lengths of alkyl chains, we synthesized other four DAPhen ligands with different substitute groups in the diamide moieties, and characterized the relationship between properties and substitute groups of DAPhen ligand. The extraction results show that three of the ligands exhibit high performance in UO22+ extraction from an acidic solution and the extracted UO22+ can be easily stripped by only using ultrapure water. Spectrophotometry titration confirms that UO22+ combined with all the four ligands in 1:1 mode. The extended X-ray absorption finestructure (EXAFS) study shows that six donor atoms comprise the first equatorial shell of the UO22+ ions bonded by the DAPhen ligands, among which two nitrogen and two oxygen atoms are from the DAPhen ligand, while other two oxygen atoms are from one nitrate ions. This article promises to provide basic data for assessing the feasibility of this kind of DAPhen ligands applied in actinides separation from nuclear wastes.
2,9-二酰胺-1,10-菲罗啉(DAPhen)配体是四价萃取剂的一个新家族,因为它们与锕系元素有很强的亲和力,并且具有 CHON 原理。在这个家族中,我们最初报道的 N,N′-二乙基-N,N′-二羟基-2,9-二酰胺-1,10-菲罗啉(Et-Tol-DAPhen)对锕系元素(铀、钍、镅、钚)的选择性优于镧系元素,因此有可能应用于群体锕系元素萃取(GANEX)工艺,实现锕系元素的群体分离。本文通过调整烷基链的长度,合成了二酰胺分子中具有不同替代基团的其他四种 DAPhen 配体,并表征了 DAPhen 配体的性质与替代基团之间的关系。萃取结果表明,其中三种配体在从酸性溶液中萃取 UO22+ 方面表现出很高的性能,而且只需使用超纯水就能轻松地剥离萃取出的 UO22+。分光光度法滴定证实,UO22+ 与所有四种配体的结合比例均为 1:1。扩展 X 射线吸收有限结构(EXAFS)研究表明,由 DAPhen 配体结合的 UO22+ 离子的第一赤道壳由六个供体原子组成,其中两个氮原子和两个氧原子来自 DAPhen 配体,另外两个氧原子来自一个硝酸根离子。这篇文章有望为评估这种 DAPhen 配体应用于从核废料中分离锕系元素的可行性提供基础数据。