S. V. Demin

Lithium isotope effects in extraction of lithium chloride by benzo-15-crown-5 in the 1,1,7-trihydrododecafluoroheptanol–water system

The extraction characteristics of the 1,1,7-trihydrododecafluoroheptanol water system have been studied for lithium chloride as the salt to be extracted and benzo-15-crown-5 as the extracting agent, as well as blank extraction of lithium chloride in this system. Single-stage lithium isotope separation factors (a) have been measured at various lithium chloride concentrations in water, and the isotope effect has been multiplied by extraction chromatography. The value of a for the Li6–Li7 pair was 1.024. The light lithium isotope is concentrated in the organic phase.

Lithium and boron isotope effects in extraction systems

Extraction characteristics of chloroform-water system were studied using lithium chloride and tetrafluoroborate as extracted salts and benzo-15-crown-5 as an extractant. Single-stage isotope separation factors (α) for lithium isotopes at different concentrations of lithium chloride in water were measured and multiplication of isotope effect was made by extraction chromatography. The magnitude of α for Li6-Li7 pair was 1.036 for chloride and 1.030 for tetrafluoroborate. Light lithium isotope is concentrated in organic phase. Extraction chromatography experiments were conducted in 1,1,7-trihydrododecafluoroheptanol-water extraction system for boron isotope separation using boric acid as extracted compound and trioctylamine as an extractant as well as in chloroform-water system with lithium tetrafluoroborate as extracted compound and benzo-15-crown-5 as an extractant. The upper assessment of α values for B10-B11 boron isotopes was found to be not larger than 1.005 for both systems.

Extraction of rare earth elements with 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene with the use of 1,1,7-trihydrododecafluoroheptanol as a solvent

Extraction of rare earth elements from nitric acid solutions in a 1,1,7-trihydrododecafluoroheptanol-water system with the use of phosphoryl-containing podand 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene (L) was studied. The content of metals in organic phase was shown to be negligible at nitric acid concentration lower 1 mol/L. Distribution ratio sharply increases with nitric acid concentration from 1 mol/L and reaches 5.5 for the yttrium subgroup elements at HNO3 concentration of 6 mol/L. The rare earth elements of the yttrium subgroup were found to be extracted much better than the rare earth elements of the cerium subgroup under the same conditions, the distribution ratios in both subgroups smoothly rise with atomic number of element. It was shown using the shift of extraction equilibrium that the M: L ratio in extracted complexes is 1: 2 irrespective of the nature of rare earth element. The structure of complex {Yb[η2-(O,O′)-L]2(η2-O2NO)2}(O2NOHNO3), whose single crystals were isolated from extraction solution, was established by X-ray diffraction study. The system can be used for the isolation and separation of rare earth elements.

Extraction of rare-earth elements by alkylated dibenzo-18-crown-6 and dicyclohexano-18-crown-6 from acid solutions

The extraction of rare-earth elements (REE) by alkylated crown ethers (dibenzo-and dicyclohexano-18-crown 6; DB18C6 and DCH18C6) from acid solutions in the chloroform-water system is studied. The extraction of the REE with DCH18C6 and its alkylated derivatives in the presence of trichloroacetic acid (TCA) is far more efficient than the extraction with DB18C6 and its alkylated derivatives or when nitric or acetic acid is used instead of TCA. The distribution coefficients for the cerium metals are far higher than for the yttrium metals. The metal: crown ether ratio in the extracted complex in all cases is 1:1.

Americium(III) sorption from multicomponent solutions by macrocyclic polyester-based sorbents

Americium sorption by crown-ether-impregnated polymeric sorbents from nitric acid solutions and multicomponent nitrate solutions that model process solutions was studied. Sorption of ballast elements by the unimpregnated Porolas-T support was studied. The sorption coefficients Kd of these elements on Porolas-T do not exceed 0.01. Sorption of the same elements by crown-ether-impregnated sorbents was also studied. Dicyclohexano-18-crown-6 (DCH18C6) and its alkyl derivatives were used. Sorption coefficients were determined for all ballast elements. At the final stage of the study, 241Am sorption coefficients of from multi-component solutions were determined. The data obtained signify the utility of crown-ether-impregnated sorbents for recovering 241Am from multicomponent technological solutions.

Control of the Extractive Power of Crown Ethers by Alkyl Substitution

Aiming to find extractants suitable for recovery of cesium from nitric acid solutions with a high sodium content, two types of alkylated derivatives of 18-crown-6 were studied. Derivatives of the first type (five compounds) were prepared by introducing alkyl substituents into the macroring. Derivatives of the second type were prepared by introducing alkyl substituents into phenyl or cyclohexyl fragments of dibenzo-18-crown-6 (DB18C6) and dicyclohexyl-18-crown-6 (DCH18C6) (16 compounds). The alkylated crown ethers exhibit different reactivity depending on the substitution mode. Introduction of two alkyl substituents into the phenyl rings of dibenzo-18-crown-6 allowed preparation of compounds ensuring the Cs/Na separation factor as high as 100 and more.

Study of isotope effect upon lithium iodide complexation with benzo-15-crown-5 in water–chloroform extraction system

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 6Li-7Li pair was 1.017. The light lithium isotope is concentrated in organic phase.

Study of lithium complexes with benzo-15-crown-5 ether by X-ray diffraction and IR spectroscopy

The complex formation of lithium with benzo-15-crown-5 (B15C5) was investigated. The complexes LiB15C5H2OX, where X = Cl− (1), I− (2), (3), (5), and LiBF4B15C5 (4) were synthesized and studied by IR spectroscopy. Complexes 1–4 were examined by X-ray diffraction. According to IR spectroscopy data, the crown ether conformation changes upon dissolution. The interaction of the extracted complex with the solvent was identified.

Structures of the compounds preparatively isolated in the extraction of rare-earth metals with 2-diphenylphosphoryl-1-diphenylphosphorylmethoxy-4-ethylbenzene

The structures of 2-diphenylphosphoryl-1-diphenylphosphorylmethoxy-4-ethylbenzene (L), its adduct with water and nitric acid, and the complex [(L)2Nd(η2-O2NO)2](NO3) · NO3 · 2C6H6 were determined by X-ray diffraction. The above compounds were isolated under conditions very similar to those used for extractive separation of rare-earth metals in the system water-1,1,7-trihydrododecafluoroheptan-1-ol with L as an extractant. Assignment of the absorption bands in the IR spectra of the single crystals obtained was performed.

Extraction of rare-earth elements by crown ethers from acid solutions into 1,1,7-trihydrododecafluoroheptanol

Extraction of rare-earth elements from acid solutions in the 1,1,7-trihydrododecafluoroheptanol-water system was studied using crown ethers: dicyclohexano-18-crown-6 (DCH18C6; isomer A) and di-tert-butyldicyclohexano-18-crown-6 (DTBDCH18C6). All other conditions being equal, the extractability of rareearth elements by DTBDCH18C6 is far higher than for DCH18C6 itself. Trifluoroacetic and trichloroacetic acids increase metal distribution ratios. The distribution ratios for the cerium rare earths considerably exceed those for the yttrium rare earths. The stoichiometry of the rare-earth complexes of crown ethers was determined. The component ratio in the extracted complexes, M: crown ether, is 1: 1 in all cases. Rare-earth separation factors are due to different stability constants of extracted complexes.