In this work, the electrochemical properties of a MnO 2 nanocomposite electrode were investigated in 1butyl-3-methyl-imidazolium hexafluorophosphate ([Bmim]PF 6 )/N,N-dimethylformamide (DMF) electrolyte. The [Bmim]PF 6 /DMF electrolyte with different volume fractions exhibits significant influence on the electrochemical properties of the electrode. When the volume ratio of [Bmim]PF 6 and DMF was 1 : 1, the electrode showed the best electrochemical performance. The operation potential window of the MnO 2 nanocomposite electrode in ionic liquids was 2.1 V and the specific capacitance according to the mass of MnO 2 was 523.3 F g À1 at 3 A g À1 . Then, a high-voltage (3 V) MnO 2 asymmetric supercapacitor was successfully fabricated, using the MnO 2 nanocomposite electrode, activated carbon and [Bmim]PF 6 /DMF as the positive electrode, negative electrode and electrolyte, respectively. The MnO 2 asymmetric supercapacitor displayed a maximum specific energy of 67.5 W h kg À1 at a specific power of 593.8 W kg À1 and a maximum specific power of 20.4 kW kg À1 at a specific energy of 8.5 W h kg À1 . The impressive results showed that [Bmim]PF 6 /DMF could be a promising electrolyte for MnO 2 supercapacitors.

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1-Methylimidazole (1-MIM) and 2-methylimidazole (2-MIM) are miscible in water and imidazolium based ionic liquids (ILs), and can coordinate with soft metal ions. This paper reports a novel solvent extraction process for trivalent lanthanides and yttrium from aqueous solutions into ILs, which was promoted by a hydrophilic 1-MIM or 2-MIM. Slope analysis confirmed that MIM in ILs formed a 1 : 1 complex with La(3+) and Y(3+) and a 1 : 4 complex with Eu(3+) and Lu(3+), depending on the atomic number of the metal and the metal-ligand interactions that have been characterized by FTIR spectroscopy and ESI-MS. The effect of nitrate concentration on the extraction of lanthanides with 1-MIM in ILs was analysed. It indicated that nitrate anions were involved in the extraction process. Under the same conditions, the extraction of lanthanides with MIM into n-pentanol was carried out. The extractability was by far lower than that obtained in ILs. Both cationic exchange and neutral solvation mechanisms occurred in ILs and only the neutral solvation mechanism occurred in n-pentanol, which were demonstrated by the extraction tests and the structure of extracted species determined by ESI-MS. The competitive extraction in ILs showed good selectivity for lanthanides compared to alkali metals and alkaline earth cations. After extraction, lanthanides could be stripped very easily from the ionic liquid phase with dilute nitric acid. From the temperature dependence data, the thermodynamic parameter values (ΔH, ΔS and ΔG) were calculated. The results indicated that the extraction reactions were spontaneous and went through an endothermic process.

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