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

• A-PzPy showed good selectivity of Am 3+ over Eu 3+ without any lipophilic anion source. • A-PzPy could effectively separate Am 3+ from Eu 3+ at a wide molar acidity range. • The composition of complexes was determined by coordination study. • A neutral complexation extraction mechanism was determined. The synthesis, Eu 3+ complexation, and selective solvent extraction of Am 3+ over Eu 3+ in nitric acid solution by 2-carboxamido-6-(1 H -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 Am 3+ than Eu 3+ 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(NO 3 ) 2 (H 2 O)∙2(Et- p -Tol-A-PzPy)](NO 3 ). Combining the results of solvent extraction and complexation study, the extraction mechanism was proposed. Furthermore, the stability constants (log β ) and thermodynamic parameters (Δ H , Δ S , Δ G ) for complexation of Eu 3+ with Et- p -Tol-A-PzPy were also presented.