Electrolytic extraction of yttrium using recycle liquid gallium electrode from molten LiCl-KCl

Abstract

To recover the rare earth element yttrium (Y) from spent fuel by molten salt electrolysis technology, the electrochemical redox mechanism of Y(III) and Ga(III) ions on tungsten electrode and the electrode reaction of Y(III) ions on the liquid Ga electrode were systematically detected by a series of electrochemical test methods, including cyclic voltammetry, square wave voltammetry and open circuit chronopotentiometry, etc. The thermodynamic and kinetic parameters of the electrode process on Ga(III) and Y(III) ions were obtained in this work. The measured diffusion activation energies (Ea) of electrode process for Y(III) and Ga(III) ions were calculated as 30.40 kJ·mol−1 and 33.33 kJ·mol−1. The electrodeposition process of Y and Ga was studied by CV and OCP, and thermodynamic parameters of Ga-Y alloys formed were also calculated. Thermodynamic parameters of Ga2Y intermetallic compounds were calculated based on open circuit chronopotentiometry at different temperatures (ΔHf0(Ga2Y)=-279.205kJmol-1 and ΔSf0(Ga2Y)=-123.9Jmol-1K-1). Yttrium was extracted by potentiostatic electrolysis and galvanostatic electrolysis on liquid Ga electrode in molten salts. In order to save the amount of liquid metal gallium, the best initial (2.5 g) was used. The cathodic deposition Products were characterized by X-ray diffraction analysis and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. According to ICP-AES analysis, the extraction rate of Y on Ga electrode can reach a maximum of 99.39%.