2-Carboxamido-6-(1H-pyrazol-3-yl)-pyridines as ligands for efficient separation of americium(III) from europium(III)

[Display omitted] •A-PzPy showed good selectivity of Am3+ over Eu3+ without any lipophilic anion source.•A-PzPy could effectively separate Am3+ from Eu3+ at a wide molar acidity range.•The composition of complexes was determined by coordination study.•A neutral complexation extraction mechanism was determined. The synthesis, Eu3+ complexation, and selective solvent extraction of Am3+ over Eu3+ in nitric acid solution by 2-carboxamido-6-(1H-pyrazol-3-yl)-pyridines (A-PzPy) ligands were described. Without the aid of any lipophilic anion source, A-PzPy ligands in methyl isobutyl ketone (MIBK) diluent demonstrated a more favorable affinity of Am3+ than Eu3+ at high acidity levels. Slope analysis showed the formation of 1:2 metal/ligand extracted species. The extraction was a spontaneous exothermic process. The analyses of fluorescence titration, Fourier transform infrared (FT-IR), Raman, time-resolved laser fluorescence spectrum (TRLFS), electrospray ionization mass spectrometry (ESI-MS), conductivity and microcalorimetric titration revealed that the composition of complex is [Eu(NO3)2(H2O)∙2(Et-p-Tol-A-PzPy)](NO3). Combining the results of solvent extraction and complexation study, the extraction mechanism was proposed. Furthermore, the stability constants (log β) and thermodynamic parameters (ΔH, ΔS, ΔG) for complexation of Eu3+ with Et-p-Tol-A-PzPy were also presented.