Trivalent Actinides/Lanthanides Separation by Nitrogen Heterocyclic Ligands

Trivalent actinides/lanthanides separation is one of key steps in partitioning and transmutation strategy, and is important for the advanced nuclear fuel cycle. However, the separation is a big challenge due to the similarities of physico-chemical properties between trivalent actinides and lanthanides. Solvent extraction has been widely studied and ligands containing soft donor atoms such as N, S have displayed good actinides selectivity over lanthanides. Nitrogen heterocyclic ligands have attracted much attention because of their relatively high separation factors and consistency with the "CHON principle" resulting in possibility of complete incineration. In this review, research progress on the typical nitrogen heterocyclic extractants in the last decade are covered, including Terpy, TPTZ, BTPs, BTBPs and TPEN series. The separation abilities and stabilities under various conditions are compared, and the extraction mechanism and impact factors of extraction ability are described. The design, optimization and prospect of the extractants are also proposed.