Solvent extraction of nitric acid, uranium(VI) and thorium(IV) by N,N,N',N'-tetrahexylsuccinylamide

A new kind of diamide N,N,N’,N’-tetrahexylsuccinylamide（THSA） was synthesized, characterized and used for the extraction of HNO3, U（VI） and TI（IV） in a diluent composed of 0.5 volume fraction 1,2,4-trimethy benzene（TMB） and 0.5 volume fraction kerosene（OK）. Extraction distribution coefficients of U（VI） and TI（IV） as functions of aque- ous nitric acid concentration, extractant concentration, temperature and salting-out agent （LiNO3 ） have been studied, and it is found that THSA as an extractant is superior to TBP for extraction of U（VI） and TI（IV）. Back extraction was also studied. At low acidity, the main adduct of THSA and HNO3 is HNO3.THSA. THSA.（HNO3）2 and THSA.（HNO3）3 are also found at high acidity. The compositions of extracted species, apparent equilibrium constants and enthalpies of extraction reactions have also been calculated.

Th(Ⅳ) and U(Ⅵ) removal by TODGA in ionic liquids:extraction behavior and mechanism,and radiation effect

Extraction behavior of thorium(Ⅳ) and uranium(Ⅵ) from nitric acid(HNO_3) was studied using N,N,N',N'-tetraoctyldiglycolamide(TODGA) as extractant in different ionic liquids, and isooctane as comparison.Slope analyses with varying HNO_3 concentrations and diluents revealed the extraction mechanism. With increasing length of alkyl chain and HNO_3 concentration, the extraction mechanism of TODGA/IL system changed from cation exchange to neutral complex and/or anion exchange,and the molar ratio between TODGA and metal ions varied gradually from 2:1 to 1:1 for Th(Ⅳ) and 3:1 to 1:1 for U(Ⅵ). The kinetics and thermodynamic studies of Th(Ⅳ)and U(Ⅵ) by the best TODGA/[C_2mim][NTf_2] system showed that the extraction equilibrium was reached within 2 h and extraction reactions were endothermic. Compared to TODGA/isooctane system, TODGA/[C_2mim][NTf_2]system presented higher radiation stability under c-irradiation. Therefore, it would have a promising application in spent fuel reprocessing.

N,N,N’,N’-四己基丁二酰胺萃取铀、钍及硝酸的机理

合成了 N,N,N?N?四己基丁二酰胺(THSA)。以正十二烷为稀释剂研究了THSA萃取硝酸的平衡,认为在低酸度下主要形成THSA·HNO3加合物,在高酸度下主要形成加合物THSA·HNO3和THSA·(HNO3)2;还研究了THSA从硝酸介质中萃取铀、钍的机理,通过考察 HNO3浓度、THSA浓度及温度对铀和钍分配比的影响,得出了萃合物的组成为UO2(NO3)2·THSA和Th(NO3)4·2THSA,并计算出萃取反应的表观平衡常数及热焓。实验结果表明THSA具有较强的对铀、钍萃取能力,并有望实现铀、钍分离。

钍(Ⅳ)、铀(Ⅵ)的N_2O_2型Schiff碱配合物的合成与性质

合成了Th(Ⅳ)、U(Ⅵ)与N,N′亚乙基二(2—羟基—3—甲氧基苯甲亚胺)和N,N′-邻亚苯基二(2—羟基—3—甲氧基苯甲亚胺)的四个Schiff碱配合物:ThL_2·XH_2O和UO_2L·H_2O(L=MSEA和MSPA,X=0,2),通过元素分析、摩尔电导、红外光谱、紫外光谱、荧光光谱、x—射线粉末衍射和差热分析,研究了配合物的组成和有关性质。