Extraction of tetravalent uranium by N,N,N',N'-tetramethylmalonamide in ionic liquid
Extraction of tetravalent uranium by N,N,N',N'-tetramethylmalonamide in ionic liquid
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DOI：
10.1016/j.seppur.2020.116629
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发表时间：
2020-01
影响因子：
8.6
通讯作者：
Zong Guo;Taiwei Chu
中科院分区：
文献类型：
--
作者：
Zong Guo;Taiwei Chu
本文采用萃取剂N,N,N',N'-四甲基丙二酰胺(TMMA)将硝酸水溶液中的四价铀(简称U(IV))萃取到离子液体1-丁基-3-甲基咪唑鎓双(三氟甲基磺酰基)亚胺([C4mim][NTf2])体系中。研究发现，与传统甲苯体系相比，[C4mim][NTf2]中U(IV)的分配系数提高至23，并且在1:1体积比下单级萃取效率超过95%。虽然浓度在 1.0 至 3.0 M 之间的硝酸溶液中很难提取 U(VI)，但在该体系中 U(IV) 和 U(VI) 可以被选择性分离，分离因子 (SFIV/VI) 可达 28。根据斜率分析，每个 U(IV) 离子可能结合一个 TMMA 分子。对于浓度在 1.0 到 3.0 M 之间的硝酸，U(IV) 的萃取过程可能遵循阳离子交换机制。研究还发现，提取到离子液体相中的U(IV)配合物非常稳定，在空气中保存至少两周而不被氧化。
In this paper, the extractantN,N,N',N'-tetramethylmalonamide (TMMA) was used to extract tetravalent uranium (abbreviated as U(IV)) from aqueous nitric acid solution into ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) system. It is found that the distribution coefficient of U(IV) in [C4mim][NTf2] is improved to 23, and the single stage extraction efficiency is more than 95% at 1:1 vol phase ratio, compared with the traditional toluene system. While U(VI) could be hardly extracted from nitric acid solutions at a concentration between 1.0 and 3.0 M, U(IV) and U(VI) could be selectively separated in this system and separation factor (SFIV/VI) could reach 28. According to the slope analysis, each U(IV) ion probably bounds one TMMA molecule. For nitric acid at a concentration between 1.0 and 3.0 M, the extraction process of U(IV) might follow the cation exchange mechanism. It is also found that the U(IV) complex extracted into the ionic liquid phase could be very stable and maintain in the air for at least two weeks without being oxidized.