In situ electrochemical investigation of the reaction progress between Zr and a CuCl–SnCl2 mixture in a LiCl–KCl molten salt

Abstract

The electrochemical behaviors of CuCl, SnCl₂ and a CuCl–SnCl₂ mixture were investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). The reduction potentials of Cu(I) and Sn(II) on CV curves are −0.49 and −0.36 V, respectively, while the reduction potentials of Cu(I)–Sn(II) in the CuCl–SnCl₂ mixture almost overlap. The co-chlorination reaction progress between CuCl–SnCl₂ and Zr was also studied by monitoring the concentration changes of Cu(I), Sn(II) and Zr(IV) ions in situ by CV, SWV and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analyses. The results indicate that during the reaction, the concentration of Zr(IV) ions increases gradually, while those of Cu(I) and Sn(II) decrease rapidly until they disappear. When the molar ratios of Cu(I) to Sn(II) are 1 : 1 and 1 : 0.5, the reaction between Cu(I) and Zr is faster but cannot exceed twice that of Sn(II) and Zr in a short time. When the theoretical product of ZrCl₄ is a constant, and with the proportion of CuCl to SnCl₂ decreasing from 1 : 0 to 0 : 1, the chlorination reaction time periods increase from 40 to 170 min. Chloride products such as Cu_xSn_y, Sn_xZr_y, and Cu_xZr_y, are formed with different molar ratios. The coupling effect caused by the formation of alloys will promote the chlorination reaction when the ratios of CuCl to SnCl₂ are 0.66 : 0.17 and 0.5 : 0.25. The results provide a theoretical basis for the electrolytic refinement of zirconium.