Effect of Diluents on The Synergistic Solvent Extraction and Separation of Trivalent Lanthanoids With 4-Benzoyl-3-Phenyl-5-Isoxazolone and <i>tert</i>-Butylcalix[4]Arene Tetrakis(N,N-Dimethyl Acetamide) and Structural Study of Gd(III) Solid Complex By IR and NMR

The solvent extraction of 14 lanthanoid(III) ions from a chloride medium with acidic chelating extractant 4-benzoyl-3-phenyl-5-isoxazolone (HPBI) and <i>tert</i>-butylcalix[4]arene tetrakis(N,N-dimethylacetamide) (S) as a synergistic agent in C<sub>6</sub>H<sub>6</sub> has been studied. In all cases, Ln(III) ions were extracted as Ln(PBI)<sub>3</sub>·S species. Positive values of the synergistic coefficients show that all lanthanoids were extracted synergistically upon the addition of compound S to the chelating extractant. The values of the equilibrium constant and the separation factors were calculated. The synergistic solvent extraction of five selected lanthanoid ions (La<sup>3+</sup>, Nd<sup>3+</sup>, Eu<sup>3+</sup>, Ho<sup>3+</sup>, and Lu<sup>3+</sup>) with a mixture of HPBI and S from a perchlorate medium in other diluents such as CHCl<sub>3</sub>, C<sub>2</sub>H<sub>4</sub>Cl<sub>2</sub>, and CCl<sub>4</sub> has been studied too. It was found that the values of the equilibrium constant increased in the order CHCl<sub>3</sub> < C<sub>2</sub>H<sub>4</sub>Cl<sub>2</sub> < CCl<sub>4</sub>. The effect of the diluents on the metal extraction and separation has been discussed. A solid complex of Gd(III) with HPBI and S was synthesized. The composition of the complex was determined as Gd(PBI)<sub>3</sub>·S using elemental analysis, IR, and <sup>1</sup>H NMR data.