Chemical-grade zirconium contains about 1–3 wt% hafnium, which is harmful for nuclear applications due to its high neutron-capture cross section. In the present paper, Zr-Hf separation in Sn-Cu-Zr-Hf and Cu-Zr-Hf alloy systems using molten salt containing CuCl₂ or CuF₂ was thermodynamically evaluated and lab-scale experiments on zirconium and hafnium separation in different molten salt systems were conducted. The best single-step Hf removal efficiency and Zr-Hf separation factor of about 95% and 9.0, respectively, were obtained with a NaCl-CaCl₂-CuCl₂ (3 wt%) molten salt system at 850°C and the CuCl₂/Hf stoichiometric ratio of 1.5.

In this paper, a detailed study of the electrochemical behavior of zirconium in the molten LiF-KF-ZrF₄ system on an inert molybdenum electrode was carried out at 600 °C. Several electrochemical techniques were employed such as cyclic voltammetry, chronoamperometry and square wave voltammetry. The reduction of zirconium was found to be a multi-step process that at the potentials of 1.15, 1.50 and 1.62 V versus Pt, the corresponding cathodic reactions of Zr⁴⁺/Zr²⁺, Zr²⁺/Zr⁺ and Zr⁺/Zr occurred. The result was further confirmed by the theoretical calculation of the number of transferred electrons according to the cyclic voltammetry and square wave voltammetry analysis. Moreover, based on the cyclic voltammograms, the diffusion coefficient of Zr⁴⁺ ions in the eutectic LiF-KF containing 1 wt% ZrF₄ at 600 °C was estimated to be about 8.31 × 10^-6 cm² s^-1. The present electrochemical study on zirconium in the molten fluoride system will be a theoretical reference for future zirconium electrorefining from Zr alloy or scraps.