Electrochemical and thermodynamic properties of europium(III), samarium(III) and cerium(III) in 1-butyl-3-methylimidazolium chloride ionic liquid Ch. Jagadeeswara Rao, K.A. Venkatesan, K. Nagarajan * , T.G. Srinivasan, P.R. Vasudeva Rao Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India article info Article history: Received 20 July 2009 Accepted 6 January 2010 Available online xxxx abstract Electrochemical behavior of trivalent lanthanides such as europium(III), samarium(III) and cerium(III) in 1-butyl-3-methylimidazolium chloride (bmimCl) was investigated by cyclic voltammetry and chronopo- tentiometry at platinum working electrode in the temperature range of 343–373 K. The cyclic voltammo- grams of these metal ions in bmimCl at Pt electrode consisted of quasi-reversible waves occurring at a cathodic peak potential of 0.769 V, 0.547 V and 0.558 V (vs. Pd, 373 K) were attributed to the reduc- tion of Eu(III), Sm(III) and Ce(III) to their respective divalent states. A prewave observed in the cyclic vol- tammogram of Eu(III) represents the reduction of Eu(III) to Eu(II) adsorbed on Pt electrode. The diffusion coefficients of these trivalents in bmimCl were determined to be of the order of 10 8 cm 2 s 1 by cyclic voltammetry and chronopotentiometry and the charge transfer rate constants (k s ) were determined to be of the order of 10 5 cm s 1 by Nicholson method. The apparent standard potentials, E 0  (vs. Cl 2 /Cl  ), and some thermodynamic properties of reaction of LnCl 3 from LnCl 2 were determined and the results are reported in this paper. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Room temperature ionic liquids (RTILs) are finding several applications in various stages of nuclear fuel cycle. RTILs are the compounds comprising completely of ions existing in liquid state at or below the boiling point of water i.e., 373 K [1,2]. They have several attractive properties suitable for aqueous and non-aqueous reprocessing applications. RTILs are being evaluated as an alterna- tive to the conventional diluent, n-dodecane, in aqueous reprocess- ing and as a substitute to the traditional high-temperature molten salts in non-aqueous reprocessing of spent nuclear fuels [3–9]. RTILs offer wide electrochemical window. From non-aqueous reprocessing point of view, Bhatt et al. [10–12] studied the electrochemical behavior of some lanthanides, La(III), Sm(III) and Eu(III) in tetra alkyl ammonium bis(trifluoromethylsulfonyl)imide ([R 4 X][NTf 2 ]) ionic liquids, where X = N,P and As. The ionic liquid, tetra alkyl ammonium bis(trifluoromethylsulfonyl)imide ([Me 4 X] [NTf 2 ]), exhibits large electrochemical window (>5 V) and based on the observation that Eu(III) present in this ionic liquid was re- duced to Eu(0), it was proposed as a substitute for high-temperature molten salts in non-aqueous reprocessing. Bhatt et al. [12] also stud- ied the reduction of La(III), Sm(III) and Eu(III) to metallic state in the RTIL, tri methyl butyl ammonium bis(trifluoromethylsulfo- nyl)imide[Me 3 NBu][NTf 2 ], and reported similar results as in the previous case. Legeai et al. [13] reported the electrodeposition of lanthanum in 1-octyl-1-methylpyrrolidinium bis(trifluoromethyl- sulfonyl)imide ionic liquid. Nagaishi et al. [14] studied the physico- chemical behavior, spectroscopic and electrochemical properties of Eu(III) as a function of water in N,N-diethyl-N-methyl- N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide (demmaNTf 2 ) and bmimNTf 2 ionic liquids. Yamagata et al. [15] studied the electrochemical behavior of samarium, europium and ytterbium in N-butyl-N-methylpyrrolidinium bis(trifluoromethyl- sulfonyl)imide (BMPyNTf 2 ), 1-ethyl-3-methylimidazolium bis(tri- fluoromethylsulfonyl)imide (emimNTf 2 ). We also investigated [16] the suitability of BMPyNTf 2 ionic liquid for the electrodeposition of lanthanides and studied the electrochemical behavior of europium(III) in the BMPyNTf 2 at various temperatures. It was found that Eu(III) underwent a single step quasi-reversible one- electron transfer to Eu(II) followed by a two-electron irreversible reduction to metallic europium at glassy carbon and stainless steel electrodes. Lin and Hussey [17] studied the electrochemical and spectro- scopic properties of cerium(III) in the basic AlCl 3 -1-methyl-3-ethy- limidazolium chloride and reported a quasi-reversible reduction of Ce(IV) to Ce(III) at glassy carbon, Pt and W electrodes. Schoebrechts et al. [18,19] studied the electrochemical behavior of some triva- lent lanthanides ions such as Sm(III), Eu(III), Tm(III) and Yb(III) dis- solved in acidic AlCl 3 -butylpyridinium chloride and reported that they were reduced to the corresponding divalent ions at the work- ing electrode. However, the electrochemical behavior of Eu(III), Sm(III) and Ce(III) in 1-butyl-3-methylimidazolium chloride ionic liquid have not been reported so far. The formal potential of 0022-3115/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2010.01.005 * Corresponding author. Fax: +91 044 27480065. E-mail address: knag@igcar.gov.in (K. Nagarajan). Journal of Nuclear Materials xxx (2010) xxx–xxx Contents lists available at ScienceDirect Journal of Nuclear Materials journal homepage: www.elsevier.com/locate/jnucmat ARTICLE IN PRESS Please cite this article in press as: C. Jagadeeswara Rao et al., J. Nucl. Mater. (2010), doi:10.1016/j.jnucmat.2010.01.005