Synergistic and antagonistic effects during solvent extraction of Gd(III) ion in ionic liquids

Study of the liquid-liquid extraction of Gd(III) ion with a series of phosphorus-containing calix[4]arenes by the well-known method of slope analysis and determination of the process parameters are presented employing three ionic liquids, ([C(1)C(n)im(+)]/[C(1)C(4)pyr(+)][Tf2N-], n = 4, 10) as diluents. The solvent extraction of Gd(III) ion with a chelating compound, 4-benzoyl-3-phenyl-5-isoxazolone (HPBI) has been investigated as well, plus various synergistic solvent systems. Enhanced extraction (synergism) and complete destruction of it by addition of excess of the two ligands are demonstrated. This antisynergistic effect or antagonism is shown to be greater than the negative effect due to the chemical nature of the IL's cation connected with the water content of the organic phase. The ligand effect on the complexation properties of Gd(III) ion is quantitatively assessed. The synergistic effect in an IL media, [C(1)C(10)im(+)][Tf2N-] is further evaluated and discussed. The organic extracts are examined by EPR and P-31 NMR approaches in order to viewing the cation coordination and ligands' binding mode in the organic phase solution. Several conclusions are given highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the stronger chelating agent HPBI for various metal s-, p-, d- and f-cations. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the liquid-liquid extraction of Gd(III) ions using a series of phosphorus-containing calix[4]arenes and three ionic liquids as diluents. The chelating compound 4-benzoyl-3-phenyl-5-isoxazolone is found to enhance the extraction, and the addition of excess ligands completely destroys the extraction. The complexation properties of Gd(III) ions are quantitatively assessed, and the role of ionic diluents in the complexation processes and selectivity is discussed.