Ultra-Efficient Americium/Lanthanide Separation through Oxidation State Control

Lanthanide/actinide separation is a worldwide challenge foratomic energy and nuclear waste treatment. Separation of americium (Am), acritical actinide element in the nuclear fuel cycle, from lanthanides (Ln) ishighly desirable for minimizing the long-term radiotoxicity of nuclear waste, yetit is extremely challenging given the chemical similarity between trivalentAm(III) and Ln(III). Selective oxidation of Am(III) to a higher oxidation state(OS) could facilitate this separation, but so far, it is far from satisfactory forpractical application as a result of the unstable nature of Am in a high OS.Herein, wefind a novel strategy to generate stable pentavalent Am (Am(V))through coordination of Am(III) with a diglycolamide ligand and oxidation withBi(V) species in the presence of an organic solvent. This strategy leads toefficient stabilization of Am(V) and an extraordinarily high separation factor (>104) of Am from Ln through one single contact insolvent extraction, thereby opening a new avenue to study the high-OS chemistry of Am and fulfill the crucial task of Ln/Amseparation in the nuclear fuel cycle. The synergistic coordination and oxidation process is found to occur in the organic solvent, andthe mechanism has been well elucidated by quantum-theoretical modeling.

Automated summary

Lanthanide/actinide separation is a worldwide challenge for atomic energy and nuclear waste treatment. This study presents a novel strategy to generate stable pentavalent Am (Am(V)) through coordination of Am(III) with a diglycolamide ligand and oxidation with Bi(V) species in the presence of an organic solvent. This strategy enables efficient stabilization of Am(V) and an extraordinarily high separation factor (>104) of Am from Ln, providing a new avenue for the high-OS chemistry of Am and fulfilling the crucial task of Ln/Am separation in the nuclear fuel cycle.