Radiolysis of N-Donor Extractants for the Hydrometallurgical Separation of Trivalent Actinides and Lanthanides

N-donor ligands are currently discussed as promising extractants in the hydrometallurgical separation of trivalent actinides (An(III)) from lanthanides (Ln(III)) in the treatment of used nuclear fuel. Due to their high selectivity for An(III) under process-relevant conditions, the separation from the chemically similar Ln(III) can be achieved with a low number of process steps (e.g., extraction/scrubbing/stripping stages). 6,6’-Bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)[2,2’]bipyridine (CyMe4BTBP) and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenantroline (CyMe4BTPhen) are prominent members, therefore their radiolytic stability against gamma radiolysis was studied in 1-octanol solution with and without contact to HNO3 solution. The radiolysis products were identified using high-resolution mass spectrometry. Semi-quantitative analyses and pulsed electron radiolysis were used to study the radiolysis mechanism for both ligands. The changing solvent extraction properties as a function of absorbed dose were studied as well. Alpha-hydroxyoctyl radical addition products were identified as the predominant radiolysis products. The results of this collaborative study will be presented and discussed.[1][1] Schmidt, H.; Wilden, A.; Modolo, G.; Bosbach, D.; Santiago-Schübel, B.; Hupert, M.; Mincher, B. J.; Mezyk, S. P.; Švehla, J.; Grüner, B.; Ekberg, C., Gamma and pulsed electron radiolysis studies of CyMe4BTBP and CyMe4BTPhen: identification of radiolysis products and effects on the hydrometallurgical separation of trivalent actinides and lanthanides. Radiat. Phys. Chem. 2021, 189, 109696