寡聚芳酰胺萃取剂分离钍和镧系离子的研究

Study on the Separation of Thorium and Lanthanide Ions by Oligoaromatic Amide Extractant

镧锕系金属离子具有极其相近的物理化学性质,其分离是核燃料循环后段中的关键环节,也是世界性的挑战,因此,找寻新型高效分离方法具有重要的研究意义。为实现镧锕系金属离子高效分离,选用了液-液萃取方法,考察了萃取剂1(寡聚芳酰胺五聚体)、2(寡聚芳酰胺三聚体)、3(寡聚芳酰胺二聚体)对La^(3+)、Ce^(3+)、Pr^(3+)、Nd^(3+)、Sm^(3+)、Gd^(3+)、Yb^(3+)、Lu^(3+)、Th^(4+)的萃取能力和影响因素,探讨了萃取剂1的萃取性能以及反萃取能力。结果显示,在选取的9种金属离子中,萃取剂1、2、3对Th^(4+)的萃取率最高,分别为88.6%、56.4%和44.1%,而对8种镧系金属离子的萃取率均较低且相差不大。萃取剂1对Th^(4+)与8种镧系金属离子的分离因子(SF)中,最大的是SF_(Th/Sm),最小的是SF_(Th/Lu),均值为21.9,具备把Th^(4+)从这9种金属离子中高效分离出来的能力,而萃取剂2和3不具备。萃取剂的配位基数量与其萃取能力成正比,且Th^(4+)所受影响最大,金属离子性质也影响着其萃取性能。随着pH值增加,萃取剂1对Th^(4+)的萃取率呈现出先升后降的变化趋势。萃取剂1和Th^(4+)的萃取饱和容量为0.105 g·L^(-1),络合比为1∶1。在盐酸浓度为2.5 mol·L^(-1)时,负载有机相萃取剂1的反萃率可达93%以上。通过研究这类新型萃取剂对镧锕系金属离子的分离性能,可为设计出更高选择性的萃取剂提供参考。

The separation of actinides from lanthanides is a critical control segment in the last stage of the nuclear fuel cycle,and it is also a worldwide challenge due to the extreme similarity of physicochemical properties of actinides and lanthanides.Therefore,it is of great significance to find a new and effective separation method.In order to realize effective separation of lanthanides and actinides,the paper employed liquid-liquid extraction method to investigate the extractability and influencing factors of extractants 1(oligoaromatic amide pentamer),2(oligoaromatic amide trimer)and 3(oligoaromatic amide dimer)for La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Gd^(3+),Yb^(3+),Lu^(3+)and Th^(4+).The extraction performance and re-extraction property of extractant 1 were discussed.The results show that among the 9 selected metal cations,extractants 1,2,and 3 had the highest extractability for Th^(4+),with 88.6%,56.4%,and 44.1%,respectively.However,their extractabilities for the 8 lanthanide ions were all low and did not differ significantly.Among the separation factor(SF)of Th^(4+)and other 8 metal ions on extractant 1,the largest separation factor is SF_(Th/Sm),the smallest separation factor is SF_(Th/Lu),and the average value of separation factor is 21.9,which has the ability to efficiently separate Th^(4+)from the 9 metal ions,while extractants 2 and 3 do not.The extractant coordination number was directly proportional to its extractability,and Th^(4+)is the most affected.The metal ion properties can affect its extractability too.The extractability of extractant 1 for Th^(4+)increased first and then decreased as the pH increased.The maximum extraction capacity and complex-ratio of extractant 1 and Th^(4+)are 0.105 g·L^(-1)and 1∶1,respectively.When the concentration of hydrochloric acid is 2.5 mol·L^(-1),the re-extractability of the loaded organic phase on extractant 1 can reach more than 93%.By studying the separation performance of the new extractants for lanthanides and actinides,it is helpful to design more excellent extractants.