In this paper, the extractant N,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 volume 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 (SF_IV/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.

本文采用萃取剂N，N，N'，N'-四甲基丙二酰胺（TMMA）从硝酸水溶液中萃取四价铀（缩写为U（IV））到离子液体1-丁基-3-甲基咪唑双（三氟甲基磺酰基）酰亚胺（[C ₄ mim] [NTf ₂ ]）体系。结果表明，与传统方法相比，U [IV]在[C ₄ mim] [NTf ₂ ]中的分配系数提高到23，单级萃取效率在体积比为1：1的情况下达到95％以上。甲苯系统。虽然很难从浓度为1.0到3.0 M的硝酸溶液中提取U（VI），但在该系统中可以选择性地分离U（IV）和U（VI）和分离因子（SF _{IV / VI}）可能达到28。根据斜率分析，每个U（IV）离子可能会结合一个TMMA分子。对于浓度介于1.0和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理。还发现提取到离子液相中的U（IV）络合物可能非常稳定，并在空气中保持至少两周而不被氧化。