Unassisted and Efficient Actinide/Lanthanide Separation with Pillar[5]arene-Based Picolinamide Ligands in Ionic Liquids

Abstract

Actinide/lanthanide separation is crucial for the development of nuclear industries, while this is largely hindered by their similar chemical and physical properties. In this work, we report solvent extraction systems comprising different pillar[5]arene-based picolinamide ligands with various substituted groups and the ionic liquid, C 4 mimNTf 2 , for efficient actinide/lanthanide separation from acidic solutions. Changing the pyridine nitrogen basicity by substituting the chlorine group (−I effect) or methoxy group (+I effect) at the para-position changes the extraction performance of the ligands substantially. The chlorine group gave negative extraction performance while the methoxy group enhanced the metal ion extraction ability by three orders of magnitude. Extraction kinetics for Am 3+ and Eu 3+ was fast, and equilibrium distribution values were reached within 15 min with all three ligands. Slope analyses suggested that the stoichiometry of the extracted complexes of Am 3+ and Eu 3+ with the three ligands is M/L 2/1, and each metal ion is extracted following the cation exchange mechanism involving the transfer of three C 4 mim + cations into the aqueous phase. Fluorescence spectroscopic investigation indicated that the extracted complexes were much distorted and ligands were directly coordinated to the metal ion with no sign of water molecules in the primary coordination sphere. The possible complexation structures of the ligands and the Eu 3+ ion were optimized by density functional theory calculations, which confirmed that the differences in the extraction ability of the ligands originate from different bonding strength between pyridine nitrogens and metal ions.

First Report on a 1-Cycle Solid-Phase Extraction Method for Selective Separation of Am3+ and Eu3+: Use of BTP-Grafted Silica Decorated on Activated Carbon

“…The separation of trivalent actinides and lanthanides is one of the most difficult tasks in separation chemistry due to their similar chemical properties. − Although much progress has been made concerning the development of extractants, the liquid–liquid extraction process has certain drawbacks, such as excess utilization of volatile organic compound (VOC)-based solvents, secondary waste accumulation, emulsion formation between phases, and multistage extraction processes, which will affect the economic performance of the process in large-scale practical applications. Alternatively, solid-phase extraction technique has been considered as a relatively “green” separation method with high separation efficiency due to the possibility of column mode operation and easy scale-up options.…”

Complexation and Separation of Palladium with Tridentate 2,6-Bis-triazolyl-pyridine Ligands: Synthesis, Solvent Extraction, Spectroscopy, Crystallography, and DFT Calculations

“…Solvent extraction-based techniques are deemed one of the most commercial and developing methods for HLLW treatment. ,, The utilization of ideal ligands can conveniently and selectively extract desired metal ions from aqueous phases to organic phases, which has many merits including high efficiency, low energy consumption, and, most importantly, feasibility for large-scale operation. , Earlier research involving palladium extraction from HLLW mainly focused on employing tributyl phosphate (TBP), carbamol ethylphosphine oxide (CMPO), diglycolamide (DGA), among others (Figure ), while these oxygen donor-based ligands showed very limited selectivity for Pd 2+ , with a considerable number of other fission products being coextracted into organic phases . The extraction selectivity was then slightly improved by employing soft S donors.…”

Formation of Complexes of f-Elements with Electron-Withdrawing N-Heterocyclic Diamides: Extraction and Solution Photophysics

“…Also, in these experiments, we used lipophilic anionic additives in the organic phase. The introduction of these additives can tune the extraction efficiency and selectivity [15][16][17][18].…”

“…Also, in these experiments, we used lipophilic anionic additives in the organic phase. The introduction of these additives can tune the extraction efficiency and selectivity [15][16][17][18]. The wide range of applications of rare-earth elements in industry and technology [19][20][21][22] has led to the need to find materials that, when interacting with ions of rare-earth elements, form stable compounds with outstanding luminescent properties [18].…”

“…The introduction of these additives can tune the extraction efficiency and selectivity [15][16][17][18]. The wide range of applications of rare-earth elements in industry and technology [19][20][21][22] has led to the need to find materials that, when interacting with ions of rare-earth elements, form stable compounds with outstanding luminescent properties [18]. Europium and terbium complexes with organic compounds can have properties such as intense luminescence with a high quantum yield and emission duration in the red or green range, respectively [23,24].…”