Electrochemical Recovering Zr from Molten Salt Using an Fe Electrode

To recover zirconium (Zr) from LiCl-KCl molten salt, the electro-reduction mechanisms and dynamic and thermodynamic properties of Zr­(IV) on W and Fe electrodes were investigated using a series of electrochemical techniques. Zr­(IV) was reduced by a continuous two-step process to form metallic Zr on the W electrode and a one-step process to form various Zr–Fe alloy compounds on the Fe film electrode. The deposition potentials pertaining to the formation of various Zr–Fe intermetallics were found more positive than those of Zr­(II)/Zr and Zr­(IV)/Zr­(II)­pairs. Furthermore, the dynamic data of the Zr­(II)/Zr pair on the W electrode and the ZrFe3/Zr­(IV) pair on the Fe film electrode were measured by linear polarization and Tafel methods. The results indicated that, with an increasing temperature, the value of the exchange current density for the two pairs increased, while the charge transfer resistance and transfer coefficient of the two pairs decreased. The thermodynamic data, for instance, the activities of Zr in Zr–Fe alloys and Gibbs free energies of the formation of Zr–Fe intermetallic compounds, were estimated using open-circuit chronopotentiometry. Furthermore, electrochemical recovering Zr was conducted using an Fe electrode by potentiostatic and galvanostatic electrolysis, which proved that the products were only ZrFe2 intermetallic compounds. The recovery efficiencies were 98.05% and 98.97%, respectively.