Investigation of Rare-Earth Electrochemistry in Molten Oxides

Molten oxides have successfully been used as electrolyte for the extraction of relatively noble metals in their liquid phase [1], offering a new paradigm in metal extraction that can mitigate GHG emissions thanks to the use of C-free electricity as well as the development of new inert anode materials [2,3]. Such developments have been possible thanks to the commensurable knowledge gained on well-established molten oxide systems that have a key role in pyrometallurgy, glassmaking or magma chemistry. Unfortunately, the perspective of extending such concept to more reactive metals extraction like the rare-earths is rapidly challenged by a surprising reality: there are only a limited amount of thermodynamic data available to describe rare-earth oxide chemistry in molten oxides. The present paper therefore offers to discuss the recent thermodynamic and electrochemical developments achieved in our laboratory on rare-earth oxides chemistry in such electrolytes. In particular, the methodology behind electrolyte design, and the results obtained in the prediction of the corresponding phase diagrams will be discussed. Recent electrochemical results obtained with the identified systems will be presented. [1] D. Wang, A.J. Gmitter, and D.R. Sadoway, J. Electrochem. Soc., 158 (6), E51-E54 (2011) [2] A. Allanore, L. Yin and D.R. Sadoway, Nature, 497 (7449), 353–356, (2013) [3] A. Allanore, Electrochimica Acta, 110, 587-592, (2013)