Room temperature ionic liquids (RTILs) are emerging diluents in solvent extraction processes. Unusual extraction behavior was reported for the extraction of fission products and actinides, when ionic liquids were used as diluents in place of customary diluents. In this report, some of the physical properties of the extractant that have to be met for its use in industrial scale liquid-liquid extraction, such as density, solubility, viscosity, and phase disengagement time were measured for TBP diluted in 1-alkyl-3-methylimidazolium hexafluorophosphate and compared with the data on 1.1 M TBP/n-dodecane. The results indicate that the RTILs investigated unsuccessfully match n-dodecane in many of the characteristics and thus their practical use, as diluent, in reprocessing seems to be questionable.

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Extraction of uranium by 1.1 M TBP dissolved in 1-octyl-3-methylimidazolium hexafluorophosphate (omimPF₆) ionic liquid (IL) as diluent has been studied as a function of concentration of nitric acid and uranium and that of temperature. The results are compared with those of extraction in 1.1 M TBP in 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆). Distribution ratios (D) for cxtraction of uranium in 1.1 M TBP/omimPF₆ were marginally less than those for extraction by 1.1 M TBP/bmimPF₆ at all nitric acid concentrations. The D values increased with increase in the concentration of nitric acid but decreased with increase in the concentration of uranium and temperature. In contrast to the behavior of 1.1 M TBP/n-dodecane, D values for uranium continued to increase even for nitric acid concentrations higher than 5 M, when IL acted as diluent. Solubility of omimPF₆ in nitric acid was 2-3 times less as compared to bmimPF₆. The overall enthalpy change (ΔH_tot) for the extraction of uranium in 1.1 M TBP/omimPF₆ was found to be more exothermic than for extraction by 1.1 M TBP/bmimPF₆. This behavior can be attributed to the lower extent of protonation of TBP in omimPF₆ phase. Viscosity of TBP/IL increased when butyl group was substituted with octyl group in IL.

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The relativistic discrete-variational Dirac-Fock-Slater (DV-DFS) method was performed to investigate the electronic structure of MgO doped with Pu or Am atoms. The differences between these systems, in particular, the participation of d-electrons and f-electrons in chemical bonding, were clarified by calculating their electronic structures. Substitution of actinide atoms was found to result in the effective charges of MgO becoming smaller, with a large charge transfer occurring as far as the second layer. It was also found that the bonding feature between the center atom and the surrounding oxygen atoms was extended to lower energy in the case of actinide (An) substituted systems. Moreover, the bonding characteristics were assigned; a bonding interaction for An6dO2p and an anti-bonding for An5f-O2p near the HOMO level. These complex effects were found to dominate the strength of the covalent bonding between MgO and actinide atoms.

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Zirconia-modified vermiculite (ZrMV) was prepared by mixing of zirconium oxycation with vermiculite followed by calcination at 523 K for two hours. Vermiculite and ZrMV were characterized by surface area and X-ray diffraction patterns. Sorption of strontium as a function of pH, strontium ion concentration, time, and temperature was studied on ZrMV, and the results were compared with those of vermiculite. The percentage sorption of strontium on vermiculite and ZrMV increased with increase in pH and lowering concentration of Sr²⁺. The rate of uptake of strontium by ZrMV was found to be much faster than that for vermiculite. The distribution coefficient of strontium on ZrMV is of the order of 10⁴ mL/g at pH 3, and the amount of strontium sorbed on ZrMV was always found to be much higher than that on the parent clay. The sorption data were fitted to Langmuir adsorption model for obtaining the sorption capacity of the sorbent. Increase of temperature increases the distribution coefficient of strontium on both ZrMV and vermiculite. Distribution of strontium on ZrMV was also determined from the groundwater samples obtained from the waste disposal site at Kalpakkam.

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Formation of Eu (III) -humate at various concentrations of Na⁺, Mg²⁺, and Ca²⁺ in a wide pH range (4<pH<8) was studied by the solvent extraction method using ¹⁵²Eu tracer. Concentrations of Na⁺, Mg²⁺, and Ca²⁺ ranged from 0.020 to 1.0 M, 10^-6 to 10^-3 M, and 10^-6 to 10^-3 M, respectively. The dependence of the stability on pH and concentrations of Na⁺, Mg²⁺, or Ca²⁺ was interpreted by considering the polyelectrolyte nature of humic acid. Concentration ratios of Eu (III) -humate complex to free Eu (III) ion in fresh water and seawater was estimated based on the relations between the stability of Eu (III) -humate complex and concentrations of Na⁺, Mg²⁺, or Ca²⁺. Speciation calculations of Eu (III) species dissolved in fresh water and seawater were conducted based on the relations. As a result, it was suggested that humate complex could be more important species of Eu (III) dissolved in fresh water compared with inorganic complexes such as carbonate and hydroxide. In seawater, however, the carbonate complex can be more important species, since Mg²⁺ and Ca²⁺ in seawater at a 10^-2 M level greatly inhibit the formation of the humate complex of Eu (III).

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An elution curve of element 104, rutherfordium (Rf), in anion-exchange chromatography has been obtained for the first time on an atom-at-a-time basis. The distribution coefficient in 5.4 M hydrofluoric acid solution has been determined to be 28±6 mL/g from the observed peak volume of the elution curve.

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The knowledge and understanding of the chemistry of the superheavy elements, especially of the early transactinides Rf, Db, and Sg and their compounds, both experimentally and theoretically, is nowadays quite extensive. While rapid chemical separations in aqueous solution were (and are) the method of choice for detailed investigations of Rf and Db, the development of gas-phase chemical separation methods have allowed first chemical studies of increasingly heavier transactinide elements such as Bh and Hs. In all cases, the separated transactinide element was unequivocally identified by observing the characteristic nuclear decay properties of one of its isotopes. The current paper will review the progress made in gas phase chemical separations of transactinide elements and highlight future perspectives.

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