Reduction of Light Rare Earths and a Proposed Process for Nd Electrorecovery Based on Ionic Liquids
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Electrodeposition of the rare-earth metals La, Sm, Nd, and Dy from solution in the ionic liquids N-butyl-N-methylpyrrolidinium bistriflimide (BMPTFSI) and trimethyl butylammonium bistriflimide (Me3NBuTFSI) was studied in this work. Both ionic liquids are hydrophobic and present a wide electrochemical window as well as satisfactory ionic conductivity, rendering them promising electrolytes for electroreduction of rare-earth elements. Cyclic voltammetry (CV) performed using a Pt electrode in a three-electrode cell revealed that the rare-earth cations could indeed be reduced to the metallic state in the above-mentioned ionic liquids. Furthermore, electrodeposition of the rare earths was realized on copper substrate under potentiostatic conditions of − 3.1 V versus Ag/0.1 M AgNO3 in acetonitrile at 25 °C for 5 h. Analysis of the electrodeposits by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) revealed that electrodeposition of the rare earths was feasible using these ionic liquids as the electrolytic medium. Finally, with the aim of identifying a sustainable metallurgical process for electrorecovery of rare earths, a two-compartment electrolytic cell was developed and tested for production of neodymium from a Nd(TFSI)3/BMPTFSI electrolyte.
KeywordsElectrodeposition Ionic liquids Pyrrolidinium Rare earths Neodymium
The research leading to these results has received funding from the European Community’s Seventh Framework Programme ([FP7/2007-2013]) under Grant Agreement No. 309373. This publication reflects only the authors’ views, exempting the Community from any liability. Project web site: www.eurare.eu.
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