Electrochemical behavior and extraction of zirconium on Sn-coated W electrode in LiCl-KCl melts

Abstract

To recover metallic Zr from LiCl-KCl melts, the electroreduction of Zr(IV) ion was studied employing a variety of electrochemical methods on W and Sn-coated W electrodes. Zr(IV) ion was reduced to metallic Zr through two consecutive steps on W electrode: Zr(IV) + 2e− → Zr(II) and Zr(II) + 2e− → Zr, whereas one-step four-electron transfer on Sn-coated W electrode, i.e, xSn + 4e− + Zr(IV) = SnxZr. The formation of different Sn-Zr intermetallic compounds SnxZr resulted in three reduction peaks occurring at more positive potential than that of Zr(IV) on the W electrode, which was detected using cyclic voltammetry (CV) and square wave voltammetry (SWV). Meanwhile, the thermodynamic data, such as partial molar Gibbs energy and activity of Zr in Sn-Zr alloys and standard molar Gibbs energy of formation for Sn-Zr compound, were evaluated by open circuit chronopotentiometry (OCP). Furthermore, galvanostatic electrolysis (GE) at 0.1 A and potentiostatic electrolysis (PE) at −0.85 V were performed on liquid Sn electrode, and electrolytic products were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Experimental results indicated that metallic Zr was recovered and Sn2Zr was prepared on liquid Sn electrode in LiCl-KCl-K2ZrF6 melts.