Influence of the First Coordination of Uranyl on Its Luminescence Properties: A Study of Uranyl Binitrate with ,-Dialkyl Amide DEHiBA and Water.

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 UO(NO)(L) as has been confirmed by extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), and time-resolved laser-induced fluorescence spectroscopy (TRLFS) measurements. In this study, the L ligands are two molecules of ,-di-(ethyl-2-hexyl)isobutyramide (DEHiBA) monoamide used to bind uranyl in its first coordination sphere. DEHiBA ligands can coordinate uranyl in either - or -position with respect to the nitrate ligands, and these two conformers may coexist in solution. 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 - and -UO(NO)(DEiBA) conformers were modeled with methods and compared to the experimental time-resolved luminescence spectra on UO(NO)(DEHiBA) systems. Moreover, the hydrated uranyl binitrate UO(NO)(HO) complexes in the same and configurations were modeled to quantify the impact of organic DEHiBA on the luminescence properties.