Time-Resolved Laser Fluorescence Spectroscopy and Extended X-Ray Absorption Spectroscopy Investigations of the N₃⁻ Complexation of Eu(III), Cm(III), and Am(III) in an Ionic Liquid: Differences and Similarities

Abstract

The complexation of the lanthanide Eu(III) and the actinides Cm(III) and Am(III) by N3- was investigated by application of time-resolved laser fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAFS) in the ionic liquid solution of C4mimTf2N (1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide). TRLFS measurements show that the interaction of azide with Eu(CF3SO3)3 and Eu(ClO4)3 results in both dynamic luminescence quenching by collisional encounters of N3- with Eu(III) and static luminescence quenching by inner-sphere complexation of Eu(III) by N3-. Hereby, the complexation of Eu-triflate by azide starts at a lower N3- concentration as compared to the perchlorate salt. The authors ascribe this phenomenon to a stronger bonding of ClO4- toward the metal ion than triflate, as well as to a stronger electrostatic repulsion of N3- by the perchlorate ligand. In both actinide samples (Cm(ClO4)3, Am(ClO4)3), the complexation with azide exhibits a clear kinetic hindrance. Nevertheless, mixed actinide-perchlorate-azide complexes are formed after several days in C4mimTf2N. The different reaction kinetics for the Ln- and An-complexation by azide may provide the opportunity for an effective separation of lanthanides from actinides in the nuclear fuel cycle by the use of N-based extractants in ionic liquid solution.

Kinetics of metal extraction in ionic liquids: Eu3+/HNO3//TODGA/[C1C4im][Tf2N] as a case study

“…On a more general aspect, questions that are currently under study in our laboratory deal with comparison of Am/Eu kinetics in the TODGA/C 1 C n imTf 2 N system, because previous limited experiments already showed that in some cases, strong differences are to be found between the reactivity and the kinetics of Am, Eu and Cm in IL solvents. 42,43 This may also help to understand why some extraction systems in ILs display slow kinetics, while others are very fast.…”

A remarkable enhancement in Am3+/Eu3+selectivity by an ionic liquid based solvent containing bis-1,2,4-triazinyl pyridine derivatives: DFT validation of experimental results

“…1 However, Naganawa et al reported an S.F. 20 Furthermore, an increase in metal ion extraction with increasing alkyl functionality in the ionic liquids in the case of Me-BTP did not support the conventional ion-exchange mechanism and an ion-pair mechanism may be proposed as given below: The lower extraction with ionic liquids having smaller alkyl groups may be attributed to a lower solubility of the bulky metal ligand ion-pair complexes containing 3 extractant molecules in the ionic liquid phase. 31 In a previous study, we reported an enhancement in the selectivity (S.F.…”

“…[10][11][12] RTILs display higher stability under α and γ radiation. 20 From the observed differential behavior between An 3+ and Ln 3+ towards the N 3 − complexation in RTIL, they mentioned the possibility of using RTIL media for Ln 3+ /An 3+ separation using the selective extractants for An 3+ . 14 It is, therefore, important to explore the use of RTILs for process applications using radioactive elements with better recycling possibilities.…”

Exploring Actinide Materials Through Synchrotron Radiation Techniques

“…The structural information of other actinide ions dissolved in ionic liquids is relatively limited. By direct dissolving Am(ClO 4 ) 3 in [BMIm][Tf 2 N], Stumpf et al found that the first coordination shell contained about 11 oxygen atoms and the second coordination shell was composed of about 3–4 chlorine or sulfur atoms. When azide was added to the system, immediate detection showed that the number of oxygen atom in the first shell decreased to nine.…”