P. Troosters and colleagues from the Belgian Nuclear Research Centre (SCK CEN), the Department of Chemistry, KU Leuven, and Studsvik Nuclear AB, Sweden, have published a new article entitled New synthetic pathway towards BTrzPhen-tetraol: a hydrophilic 2,9-bis-triazolyl-1,10-phenanthroline ligand for selective americium stripping. The article is published in the February 2025 issue of Dalton Transactions by the Royal Society of Chemistry.
Selectively separating Am(III) from nuclear waste streams is an extremely challenging task due to the presence of the trivalent lanthanides and Cm(III). 1,10-Phenanthroline ligands decorated with 1,2,4-triazines or 1,2,3-triazoles have emerged as promising extractants for achieving such separation. In this article, a new robust synthetic pathway towards the hydrophilic, CHON compliant bistriazoylphenanthroline ligand BTrzPhen-tetraol is reported. BTrzPhen-tetraol was synthesised both as the hydrochloride and as a free base with overall yields of 66% and 48%, respectively. The ligand demonstrated excellent solubility and stability in dilute nitric acid solutions, with no observable decomposition after three days in 0.5 mol L−1 HNO3 at 50 °C. Additionally, it exhibited rapid stripping kinetics for Am(III) and Eu(III). Liquid–liquid extraction experiments conducted with BTrzPhen-tetraol, TODGA, and radiotracers of Am(III), Cm(III), and Eu(III) yielded maximum Eu(III)/Am(III) and Cm(III)/Am(III) separation factors of 84 and 2.4, respectively, at 0.26 mol L−1 HNO3. Notably, the separation factors achieved with BTrzPhen-tetraol are comparable to those of existing systems. While only a minor influence of the BTrzPhen concentration on the distribution ratios of Am and Cm was observed under the given conditions, these results highlight the effectiveness of hydrophilic BTrzPhen ligands for selective americium stripping and encourage further optimisation to enhance performance.
Reference
https://doi.org/10.1039/d4dt03399j
Acknowledgements
The authors acknowledge funding from the Energy Transition Fund (ASOF project) and SCK CEN’s Academy. T. O. acknowledges KU Leuven for a postdoctoral mandate (PDM/20/091) and Dr Joice Thomas for the valuable discussions during the initiation of this work. W. D. acknowledges financial support from KU Leuven (Project C14/19/78). We acknowledge FWO-Vlaanderen infrastructure grants I002720N and I001920N. Mass spectrometry was made possible by the support of the Hercules Foundation of the Flemish Government (20100225-7). The authors thank Bart Van Huffel for assistance with NMR measurements, Jef Rozenski for conducting HRMS measurements, and the Radiochemical Analysis Group at SCK CEN for performing ICP-MS analyses.
