Actinide–lanthanide co-extraction by rigidified diglycolamides

<p>Within the actinide and lanthanide co-extraction strategy, three rigidified diglycolamides, namely 2,6-bis (<i>N</i>-dodecyl-carboxamide)-4-oxo-4<i>H</i>-pyran (<b>1</b>), 2,6-bis-[<i>N</i>-(4-<i>tert</i>-butylphenyl)carboxamide]-4-oxo-4<i>H</i>-pyran (<b>2</b>), 2,6-​bis[(<i>N</i>-docecyl-<i>N</i>-methyl)carboxamide]-​4-methoxy-​tetrahydro-pyran (<b>3</b>), were synthesized. Moreover, the effect of structural rigidification on Am(III) and Eu(III) extraction under different conditions was investigated. The carboxamide extractant <b>3</b> resembles the extracting behavior of <i>N,N,N</i>′,<i>N</i>′‐tetraoctyl diglycolamide (TODGA) in terms of efficiency and affinity within the lanthanide family, together with fast kinetics and satisfactory cation back-extraction. The presence of 1-octanol in the diluent mixture strongly affects the ligand stability. Moreover, despite the low extraction efficiency showed by <b>1</b> and <b>2</b>, all the three ligands exhibit a higher affinity for Am with respect to TODGA, resulting in a lower lanthanide/Americium separation factor, of around 4 for ligand <b>3</b> and close to 1 for ligands <b>1</b> and <b>2</b>.</p