Influence of the first coordination of uranyl on its luminescence properties: study of uranyl binitrate with N,N-dialkyl amide DEHiBA and water

24 August 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Uranyl binitrate complexes have a particular interest in the nuclear industry, especially in the reprocessing of spent nuclear fuel. The modified PUREX extraction process is designed to extract U(VI) in the form of UO2(NO3)2(L)2 as it has been confirmed by EXAFS, XRD and TRLFS measurements. In this study, the L ligands are two molecules of N,N-di-(ethyl- 2-hexyl)isobutyramide (DEHiBA) monoamide used to bind uranyl in its first coordination sphere. DEHiBA ligands can coordinate uranyl in either trans- or cis-positions with respect to the nitrate ligands and these two conformers may co-exist in solution. In order to use luminescence spectroscopy as a speciation technique, it is important to determine whether or not these conformers can be discriminated by their spectroscopic properties. To answer this question, the spectra of trans- and cis-UO2(NO3)2(DEiBA)2 conformers were modeled with ab initio methods and compared to the experimental time-resolved luminescence spectra on the UO2(NO3)2(DEHiBA)2 systems. Moreover, the hydrated uranyl binitrate UO2(NO3)2(H2O)2 complexes in the same trans and cis configurations were modeled to quantify the impact of organic DEHiBA on the luminescence properties.

Keywords

uranyl
fluorescence spectroscopy
ab initio

Supplementary materials

Title
Description
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Supplementary data
Description
Relative free energies for the various uranyl-nitrate complexes isomers
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