Comparison of the electrochemical behavior of some Rare Earth Elements in butyl methylpyrrolidinium dicyanamide ionic liquid
Résumé
To evaluate the feasibility of developingan efficient electrochemical separation process for rare earth elements (REE) at room temperature, the electrochemical behavior of some representative REE was evaluated in butyl methylpyrrolidinium dicyanamide (BMPyr-DCA), a room temperature ionic liquid. Because of their chemical properties,their commercial availability and their technological applications, yttrium, lanthanum, neodymium and samarium were selected for this study. The differences intheelectrochemical properties of these elements as trivalent salts in BMDCA solutions were evaluated by cyclic voltammetry using a Pt electrode underanAr atmosphere. For the elements withchemical properties that predict only the reduction in one stage (Y, La and Nd), theresults exhibitedthe simultaneous reduction of BMPyr-DCA and the REE cation andthe corresponding oxidation of the reduced REE at anodic potentials that were dependent on the REE cation. ForSm, a two-stepreduction process from Sm(III) to Sm(II) and from Sm(II) to Sm(0) wasobserved,and a clear cathodic peak wasobserved far from the cathodic electrochemical window limit (-1.38 and-2.25 Vvs Fc/Fc+); only oneanodic peakwasobserved at -0.93 V,amore negative potentialthanfor the other studied REE. The results show the same behavior as observed in other media (aqueous and molecular mediaand molten salts) and allow for the evaluation ofthe possibilityofselectively identifyingthe studied REE in the contextof their differingelectrochemical responses.
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