guest ::
| Home > Publications database > Spectroscopic characterization of f-element complexes with soft-donor ligands for selective Americium separation |
| Home > Publications database > Spectroscopic characterization of f-element complexes with soft-donor ligands for selective Americium separation |
| Conference Presentation (Other) | FZJ-2022-03476 |
; ;
2022
Abstract: BackgroundIn recent years, much effort has been invested in recycling of minor actinides from PUREX raffinate solutions. Hydrophilic N-donor ligands such as tetraso-dium-3,3',3'',3'''-([2,2'-bipyridine]-6,6'-diylbis(1,2,4-triazine-3,5,6-triyl))tetra-benzenesulfonate (SO3-Ph-BTBP) were used for selective separation of Am(III) from Cm(III) and other trivalent fission lanthanides by smart combination with diglycolamide ligands as extractants such as N,N,N',N'-tetra-n-octyl diglycola-mide (TODGA) (Geist & Panak, 2021; Wagner et al., 2016). In this present funda-mental oriented work, the combination of SO3-Ph-BTBP with TODGA and its mono- and dimethylated derivates Me-TODGA and Me2-TODGA was investi-gated for their extraction and complexation behavior in nitric acid solution.MethodExtraction studies were carried out using TODGA, Me-TODGA and Me2-TODGA as extractants in n-dodecane and SO3-Ph-BTBP in different nitric acid concentra-tions (0.05 - 4.1 mol L-1) containing all Ln(III) (except Pm, +Y) as well as 152Eu(III), 241Am(III) and 244Cm(III) as radioactive tracers (A/O = 1, mixing time = 15 min at 2500 rpm, 22°C ±1°C). After centrifugation, distribution ratios were determined measuring samples of both phases using gamma and alpha spectrometry as well as ICP-MS. Speciation studies of f-element complexes with SO3-Ph-BTBP were conducted via UV/Vis spectrophotometric titrations using different HNO3 con-centrations.ResultsAll systems showed a high selectivity of An(III) over light Ln(III), and Am(III) over Cm(III). Separation factors decreased in the order TODGA > Me-TODGA > Me2-TODGA. Moreover, a significant drop in distribution ratios of heavier lanthanides (Tb-Lu) was observed in all three extraction systems. This effect was further elu-cidated by UV/Vis speciation studies of the formed complexes with several lan-thanides. The formation of 1:2 complexes (metal-to-ligand ratio) with SO3-Ph-BTBP was confirmed for the studied lanthanides and stability constants log β of 7.7 ± 0.8 for Nd(III) at 10-3 mol L-1 HNO3 and 6.1 ± 0.4 for Ho(III) at 3 mol L-1 HNO3were determined. No complexation was observed for Nd(III) at 3 mol L-1 HNO3. Therefore, the formation of complexes with a protonated form of SO3-Ph-BTBP seems to be possible with Ho(III), but not with Nd(III). This result provides a first explanation for the unusual extraction behavior of the heavier lanthanides.ConclusionsThe combination of the water-soluble N-donor ligand SO3-Ph-BTBP with different diglycolamides as extractants allows the selective separation of Am(III) from Cm(III) and light Ln(III). In contrast, the heavier Ln(III) appear to form stronger complexes with SO3-Ph-BTBP, especially at elevated HNO3 concentrations.ReferencesGeist, A., & Panak, P. J. (2021). Recent Progress in Trivalent Actinide and Lanthanide Solvent Extraction and Coordination Chemistry with Triazinylpyridine N Donor Ligands. Solvent Extr. Ion Exch., 39(2), 128-151. https://doi.org/10.1080/07366299.2020.1831235Wagner, C., Müllich, U., Geist, A., & Panak, P. J. (2016). Selective Extraction of Am(III) from PUREX Raffinate: The AmSel System. Solvent Extr. Ion Exch., 34(2), 103-113. https://doi.org/10.1080/07366299.2015.1129192
|
The record appears in these collections: |