Time-Resolved Laser Fluorescence Spectroscopy Study of the Coordination Chemistry of a Hydrophilic CHON [1,2,3-Triazol-4-yl]pyridine Ligand with Cm(III) and Eu(III)

Abstract

The complexation of Cm(III) and Eu(III) with the novel i-SANEX complexing agent 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PTD) was studied by time-resolved laser fluorescence spectroscopy (TRLFS). The formation of 1:3, 1:2, and 1:1 metal/ligand complexes was identified upon increasing PTD concentration in 10 mol/L HClO and in 0.44 mol/L HNO solutions. For all these complexes, stability constants were determined at different acid concentrations. Though under the extraction conditions proposed for an An/Ln separation process, that is, for 0.08 mol/L PTD in 0.44 mol/L HNO, 1:3 complexes represent the major species, a significant fraction of 1:2 complexes was found. This is caused by ligand protonation, and results in lower Eu(III)/Am(III) separation factors compared to SO-Ph-BTP, until now considered the i-SANEX reference ligand. Focused extraction studies performed at lower proton concentration, where the 1:3 complex is formed exclusively, confirm this assumption.

Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process

“…This solvent has sufficient plutonium loading capacity (>30 g/L at 5 mol/L HNO 3 ) and significantly lower distribution ratios for some fission products and has the potential to replace the current EURO-GANEX solvent. Further investigations address the replacement of the sulfur containing stripping agent, SO 3 -Ph-BTP, with a CHON [49] compound such as a hydrophilic 2,6-bis-triazolyl-pyridine [50][51].…”

Optimization and Single-Stage Centrifugal Contactor Experiments with the Novel Hydrophilic Complexant PyTri-Diol for the i-SANEX Process

“…Its tridentate N donor chelating unit has been conceived in order to enhance MA(III)/Ln(III) selectivity and hydrophilicity was achieved by functionalization with alkyl chains bearing hydroxyl groups. The fulfilment of the above described requirements has already been demonstrated, in particular concerning MA(III)/Ln(III) selectivity and stability towards radiolysis by means of batch solvent extraction, spectroscopic complexometric titration and analytical chemistry experiments [42,43].…”

“…Additionally, the influence of PyTri-Diol concentration on the distribution ratios of trivalent Am and Ln was studied. For this purpose, weighted amounts of PyTri-Diol were dissolved in shown at process conditions [43]. This apparent inconsistency has been previously highlighted in other studies on different hydrophilic complexing agents [38,48,49] and is the order to study the influence on the distribution ratios of co-extracted elements.…”

2,6-Bis(1-alkyl-1H-1,2,3-triazol-4-yl)-pyridines: selective lipophilic chelating ligands for minor actinides

“…In particular, the r-SANEX (regular-Selective ActiNide EXtraction), 1c-SANEX (1cycle-SANEX) and i-SANEX (innovative-SANEX) processes have been developed to separate trivalent MA from the high active raffinate downstream of DIAMEX (DIAMide EXtraction) or PUREX (Plutonium URanium Extraction)-like processes using lipophilic heterocyclic aromatic N-donor BTP (bis-triazinyl-pyridine), BTBP (bis-triazinyl-bipyridine) and BTPhen (bis-triazinyl-1,10-phenanthroline) ligands and their hydrophilic sulfonated versions, respectively [9][10][11][12]. Among the hydrophilic complexants considered up to now for implementation in i-SANEX process, the PyTri (2,6-bis(1H-1,2,3-triazol-4-yl)-pyridine) ligands resulted to be highly selective for actinides (SF Eu/An ≈ 60-150) and endowed with an extremely high radiolytical and chemical stability [13,14]. It is worth noting that PyTri-Diol is the first CHON compliant complexant suitable for industrial implementation, since it proved to be able to achieve the An/Ln separation in centrifugal contactor device [15].…”