Nuclear energy provides about 11% of the world's electricity from about 450 power reactors.1 It is one of the world's largest sources of low-carbon power which is free from greenhouse gases or other environmental contaminants and hence this has been profoundly considered as a solution for mitigating climate change.2 However, the central bottleneck is the disposal of radioactive waste which is one of the major drawbacks inhibiting the widespread acceptance of nuclear energy.3,4 Existing methods for the purification and recovery of actinides are based on a very well-known PUREX (Plutonium Uranium EXtraction) process.5 Another method is the pyrochemical reprocessing method in which the actinides are separated from the high-temperature molten salt media electrochemically.6,7 There are, however, many disadvantages associated with the above traditional methods viz. a lot of aqueous radioactive waste generation, the requirement of high temperature and the strongly corroding nature of the molten salt media.8–10 Hence, the suitability of these methods has thus been critically questioned for the purification and recovery of nuclear fuel materials. Thus, it warrants the development of alternative approaches that could lend a hand to solve several concerns with the current methodology including non-proliferation issues, criticality, safety, apparatus corrosion, and stiffness of the process.

In recent years, room temperature ionic liquids (RTILs) have been considered for several applications including the separation of lanthanides and actinides.11 This has been primarily attributed to the unique physical properties of the ionic liquids and more importantly, their less corrosive nature and lower operating temperatures. The solubility, coordination and speciation of f-block elements in ionic liquids have been recently explored.12–15 In spite of the usage of ionic liquids for the separation of f-block elements, the primary issue of poor solubility of lanthanides and actinides in ILs is still unsolved...

Let us now discuss our attempts towards electrochemical deposition of the dissolved plutonium from [Hbet][NTf2] medium. The plutonium was deposited at a stainless steel planchette by applying a cathodic potential of −1.5 V, employing controlled potential coulometry. The alpha spectrum of the stainless steel planchette recorded after the deposition of plutonium is given in Fig. 3.

Fig. 3 Alpha spectra of the stainless steel planchette after the electrochemical deposition of plutonium.

The alpha spectrum shows that there are two characteristic peaks at energies 5.157 MeV and 5.499 MeV, respectively for 239,240Pu and 238Pu isotopes. No other peaks corresponding to other actinides viz. U, Th or Np were seen in the spectrum. There is a possibility of spectral interference of 241Am (Eα = 5.486 MeV) at 5.499 MeV alpha energy, however, the observed gamma spectrum of the sample confirms the absence of 241Am (the 59.54 keV peak is absent). The tailing of the alpha energy in Fig. 3 is attributed to the deposition of a higher concentration of plutonium on the planchette, which leads to the loss of kinetic energy of alpha particles within the source itself. The outcome of the above results clearly reveals that the dissolved plutonium can be quantitatively recovered from the ionic liquid medium via electrochemical reduction...

Note added in proof: After the present manuscript was accepted for publication, we noticed the most recently published work of Qin and co-workers27 wherein the authors have reported the separation of lanthanide oxides from actinide oxides through the carboxyl-functionalized ionic liquid, [Hbet][Tf2N]. They claim that lanthanide oxide is dissolved in [Hbet][Tf2N] selectively whereas the dissolution of uranium is found to be negligible at the temp of 40 °C. We however claim in the present study that plutonium oxide can be remarkably dissolved in the same ionic liquid [Hbet][Tf2N] at elevated temperature. The differences in the dissolution process can be attributed to the different operating temperature.