Thermodynamic study of Am(III) and Eu(III) extraction by iso-butyl-bis-triazinyl-pyridine

In order to better understand the extraction mechanisms of An(III) and Ln(III) by bis-triazinyl-pyridines (Btp), as well as the affinity of the latter towards An(III), the extraction of 152Eu and 241Am by 2,6-bis(5,6-iso-butyl-1,2,4-triazin-3-yl)-pyridine (iBu-Btp) was deeply studied. The distribution ratios (DM) of both radiotracers were determined by γ spectrometry. The analyses of the slopes of ''log-log'' plots of experimental DM values vs the concentration of iBu-Btp or that of nitrate anions at equilibrium, allowed the stoichiometry of the extracted complexes to be estimated. The extraction constants of Eu(III) and Am(III) were thereafter calculated at different temperatures and thermodynamic data, such as ΔHex and ΔSex, were deduced from the Van't Hoff's law. (author)