O,O′-dialkyl(5-ethyl-2-hydroxyphenyl)phosphonates (HL) in combination with the synergistic additive, trioctylphosphine oxide (TOPO), were considered as lithium-selective extractants for the first time. The possibility of these compounds to exhibit lithium-selective properties in the extraction of alkali metals (Li, Na, K) was predicted by quantum chemical calculations, the results of which were confirmed by extraction experiments. It is shown that the composition of the extracted species can vary depending on the extraction conditions. At the same time, O,O′-dialkyl(5-ethyl-2-hydroxyphenyl)phosphonates can participate in extraction both as cation-exchange extractants and as neutral extractants, competing with TOPO.

Федеральное государственное бюджетное учреждение наукиИнститут неорганической химии им.А. В. Николаева Сибирского отделения Российской академии наук

2-Hydroxy-5-methoxyphenylphosphonic acid (H 3 L 1 ) and the complex [Cu(H 2 L 1 ) 2 (H 2 O) 2 ] were synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. The polyhedron of the copper atom is an axially elongated square bipyramid with oxygen atoms of phenolic and of monodeprotonated phosphonic groups at the base and oxygen atoms of water molecules at the vertices. The protonation constants of the H 3 L 1 acid and the stability constants of its Cu 2+ complexes in water were determined by potentiometric titration. The protonation constants of the acid in water are significantly influenced by the intramolecular hydrogen bond and the methoxy group. The H 3 L 1 acid forms complexes CuL ‒ and CuL 2 4‒ with Cu 2+ in water.

An IR spectroscopic investigation of extraction system components was carried out to study the complexation in the extraction of acetic, monochloroacetic, dichloroacetic, and trichloroacetic acids into benzo-15-crown-5 in chloroform. It was shown that acid extraction into chloroform (blank extraction) may give adducts via two mechanisms involving either the chloroform hydrogen atom and the carbonyl oxygen of the acid or the chloroform hydrogen atom and the chlorine atom of the chloroacetic acids. A spectral criterion for the complexation with benzo-15-crown-5 was proposed. It was shown that the extractable complexes incorporate water molecules.

To study the complexing processes occurring in the extraction systems, the extraction of acetic, propionic (methylacetic), monochloroacetic, dichloroacetic and trichloroacetic acids using benzo-15- crown-5 as an extractant is considered. The extraction isotherms of acids with the pure solvent and 1 M benzo-15-crown-5 in chloroform are determined. The dependences of the distribution ratios of the considered acids on the extractant concentration in the organic phase are presented. Based on the experimental data and the “blank” extraction isotherm equations, the acid: benzo-15-crown-5 ratio in the complexes formed in the extract have been calculated (minus the contribution of extraction with the pure solvent). No complexation of methylacetic acid with benzo-15-crown-5 occurs, and the stability of the complexes of chloro-substituted acetic acids rises in the order acetic acid < monochloroacetic acid < dichloroacetic acid < trichloroacetic acid.

The complex formation of lithium thiocyanate with benzo-15-crown-5 (B15C5) was studied. The possibility of formation of both anhydrous and crystal water-containing complexes was demonstrated. The complexes LiB15C5NCS and LiB15C5H 2 ONCS were synthesized and characterized by X-ray diffraction and IR spectroscopy.

Extraction characteristics of chloroform–water system in lithium iodide extraction with benzo-15-crown-5 (B15C5) were studied. The complexation of the crown ether with LiI in organic phase was shown by IR spectroscopy. Isotope effect multiplication was performed by extraction chromatography technique. The magnitude of isotope separation factor (α) for 6 Li- 7 Li pair was 1.017. The light lithium isotope is concentrated in organic phase.