Highly Efficient\nRemoval of Americium(III) from High-Level\nWaste Using Novel Phenanthroline Diamide Ligands

The most important problem of atomic energy is the reprocessing\nof spent nuclear fuel and management of high-level radioactive waste\n(HLW). The separation of americium(III) from HLW remains a severe\nproblem, the solution of which is necessary for the sustainable development\nof nuclear energetics. Two novel phenantrolinediamide ligands having\nmethyl groups in the <i>ortho</i>-positions of the aryl\nfragments demonstrate record values for the separation factors of\nAm(III) and light lanthanides(III) including HLW imitator solution\ncontaining 10.7 g/L of lanthanides(III), 0.5 g/L of Pd, and 0.2 g/L\nof Zr in 3 mol/L nitric acid solution. They also have a high extraction\nequilibrium rate, high radiolytic stability, and fully reversible\nextraction, which allows americium back-extraction to be performed\nusing dilute nitric acid. The mechanism of complexation using SC-XRD\nand DFT calculations was investigated to demonstrate the importance\nof formation complexes having a ligand:metal 2:1 ratio.