The electrochemical oxidation behavior of Ce(III) in nitric acid and sulfuric acid media with various concentrations and compositions were investigated by cyclic voltammetry (CV) and potentiostatic electrolysis. In nitric acid media, the peak potential separation for the redox reactions of the Ce(III)/Ce(IV) couple shifted to base side with the increasing concentration of nitric acid from 1 to 6 M. The kinetics of the Ce(III)/Ce(IV) couple is rapid in high concentration nitric acid. The formal potential is independent of both proton and nitrate concentrations while the standard rate constant increases with added protons but is independent of nitrate concentration. Constant-potential electrolysis also shows that a high proton concentration is electrochemically favorable for the electron transfer of the Ce(III)/Ce(IV) couple and for a high Ce(IV) yield in nitric acid media. The current efficiency was ca. 75% for the oxidation process of Ce(III) at 298 K. A Ce(IV) yield of ca. 80% was achieved for the electrolysis of 100 mM Ce(III) in 6 M HNO 3 solution. In sulfuric acid media, the peak potential separation for the redox reactions of the Ce(III)/ Ce(IV) couple shifted to noble side with rising concentration of sulfuric acid from 0.1 to 2 M and then shifted to base side with further increase in the concentration. A Ce(IV) yield of ca. 95% was achieved for the potentiostatic electrolysis of 100 mM Ce(III) in 3 M H 2 SO 4 solution.

Extraction efficiencies of Pd(ii), Rh(iii), and Ru(iii) from HNO3(aq) to [Hbet][Tf2N] were demonstrated, i.e., Pd(ii) is the most extractable, Rh(iii) is medium extractable, and Ru(iii) is the least extractable. The extraction seems to proceed through coordination of betaine to the metal ions and the cation exchange of the formed complex with H(+).

Reduction of U(VI)O(2)Cl(4)(2-) in a mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and its chloride at E°' = -0.996 V vs Fc/Fc(+) and 298 K affords U(V)O(2)Cl(4)(3-), which is kinetically stable and exhibits typical character of U(V) in the UV-vis-NIR absorption spectrum.

Extraction behavior of U(VI) species from aqueous HNO 3 solution to [Hbet][Tf 2 N] or [TMPA][Tf 2 N] phase (Hbet: betainium, TMPA: N,N,N-trimethyl-N-propylammonium, Tf 2 N: bis(trifluoromethylsulfonyl)imide) has been studied. It was found that the extractability (E) is 62% in the extraction from 0.01 M HNO 3 to [Hbet][Tf 2 N] and decreases with an increase in [HNO 3 ] and that the U(VI) species are not extracted into [TMPA][Tf 2 N] phase. These results suggest that the extraction of U(VI) species is due to the complex formation of UO 2 2+ with the COO ¹ group of deprotonated betaine (bet). Furthermore, other metal species such as Na(I) and Al(III) in 0.01 M HNO 3 solution were found to be hardly extracted.Recently, functionalized ionic liquids (ILs), so-called taskspecific ILs (TSILs), which incorporate functional groups designed to impart to them particular properties or reactivity, have been synthesized and applied in various fields.19 In the nuclear industry, ILs and TSILs are expected to be used as media for radioactive waste treatment and the reprocessing of spent nuclear fuels, i.e., as alternative media to organic solvents for liquidliquid extraction and to molten salts for pyro-reprocessing processes. Hence, the dissolution properties of uranium oxides (UO 2 and U 3 O 8 ) into ILs, the extraction behavior of uranyl species from aqueous solutions to IL or TSIL phases, electrochemical properties of uranyl species in ILs, and properties of some other actinoid species in ILs have been studied extensively. 1027We have also studied dissolution behavior of uranium oxides (UO 2 and U 3 O 8 ) and electrochemical properties of uranyl species in BMI (1-butyl-3-methylimidazolium)- In order to develop the above processes, it is necessary to confirm as a basic matter whether the U(VI) species can be selectively extracted to the [Hbet][Tf 2 N] phase without adding any extractant. There are many reports related to the extraction of U(VI) species using ILs. However, most of them have proposed methods requiring extractants in the IL phases for the selective extraction of U(VI). 3644In this study, we examined the extraction behavior of U(VI) species from aqueous HNO 3 solutions to [Hbet] Similarly, the extraction behavior of Na(I) and Al(III), which are main components of NaF and Al 2 O 3 adsorbents, was also examined.Dried

Dependency of extraction behavior of inert platinum group metals (PGMs) like Ru­(III) and Rh­(III) on temperature has been investigated in a biphasic system consisting of HNO3(aq) and betainium bis­(trifluoromethylsulfonyl)­amide ([Hbet]­[Tf2N]) ionic liquid. The extraction reactions of Ru­(III) and Rh­(III) took 3.5 days and 113 days, respectively, at 298 K, while equilibrated within 1 and 3 h to reach 99.2% and 96.5% extraction at 353 K. Further mechanistic studies clarified that the complexation of these PGMs and [Hbet]+ is rate-determining in their extraction and that it is successfully accelerated and enhanced by elevating the temperature.