Investigation on the reaction progress of zirconium and cuprous chloride in the LiCl–KCl melt

Effects of F- on the Electrochemical Behavior of Zr(IV) and the Nucleation Mechanism of Zr in the LiCl-KCl-K2ZrF6 System

To determine the effect of F^- on the electrochemical formation of Zr, the reduction mechanism, kinetic properties, and nucleation mechanism of Zr(IV) were compared in the LiCl-KCl-K₂ZrF₆ system before and after the addition of F^- at different concentration ratios of F^-/Zr(IV). As indicated by the results, when the ratio of F^-/Zr(IV) ranged from 7 to 10, the intermediate state Zr(III) was detected, and the reduction mechanism of Zr(IV) was converted into Zr(IV) → Zr(III) → Zr. The diffusion coefficients of Zr(IV), Zr(III), and Zr(II) decreased with an increase in the value of F^-/Zr(IV). The exchange current density (j₀) of Zr(II)/Zr exceeded that of Zr(III)/Zr, and the j₀ and α values of Zr(III)/Zr decreased with the increase of F^-/Zr(IV). The nucleation mechanism at different ratios of F^-/Zr(IV) was investigated through chronoamperometry. The result suggested that the nucleation mechanism of Zr varied with the overpotential at F^-/Zr(IV) = 6. The addition amount of F^- led to the variation of the nucleation mechanism of Zr, i.e., progressive nucleation when F^-/Zr(IV) = 7 and instantaneous nucleation when F^-/Zr(IV) = 10. Zr was prepared through constant current electrolysis at different concentrations of F^- and then analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM), suggesting that the concentration of F^- can exert a certain effect on the surface morphology of products.

Preparation and Application of a NaCl-KCl-CsCl-Cs2ZrCl6 Composite Electrolyte

Using ternary molten salt with a molar ratio of NaCl:KCl:CsCl = 30:24.5:45.5 and ZrCl₄ as raw materials to prepare a NaCl-KCl-CsCl-Cs₂ZrCl₆ composite electrolyte. Characterizing by XRD, ICP-AES, optical microscopy and SEM-EDS, the results showed that when the molar ratio of CsCl:ZrCl₄ ≥ 2:1, Cs₂ZrCl₆ was generated according to the stoichiometric reaction; when the molar ratio of CsCl:ZrCl₄ < 2:1, CsCl in molten salt was almost completely converted to Cs₂ZrCl₆, and there was a ZrCl₄ phase. When the molar ratio of CsCl:ZrCl₄ = 2:1, with the increase of the reaction temperature and reaction time, the concentration of zirconium ions first increased and then decreased. The optimized preparation process conditions are: the 2:1 molar ratio of CsCl to ZrCl₄ in NaCl-KCl-CsCl, 500 °C of reaction temperature of and 3 h of reaction time. Under this condition, 99.68% conversion rate from ZrCl₄ to Cs₂ZrCl₆ was obtained. Taking the prepared NaCl-KCl-CsCl-Cs₂ZrCl₆ composite electrolyte as a raw material, a preliminary study of molten salt electrolytic refining zirconium was carried out, and a refined zirconium product with a dendrite of 10.61 mm was obtained under the conditions of a zirconium ions concentration of 5%, an electrolysis temperature of 750 °C, a current density of 0.1 A/cm², and an electrolysis time of 9 h, indicating that the composite electrolyte can be used for the electrolytic refining of zirconium.

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

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 _x Sn _y , Sn _x Zr _y , and Cu _x Zr _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.

Electrochemical behavior of zirconium in molten LiF–KF–ZrF4 at 600 °C

The Zr electrochemical behavior was investigated in the LiF–KF–ZrF₄ system and a multi-step redox mechanism was observed.

Investigation of the reaction progress between stannous chloride and zirconium in molten LiCl–KCl

LiCl–KCl–ZrCl₄ melt was prepared by displacement reaction between SnCl₂ and Zr, and the reaction progress was electrochemically monitored.