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

Abstract

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.