Separation and purification of Zr from a low-temperature LiCl–KCl–CsCl eutectic by the formation of dendritic crystal

Abstract Zirconium is widely used in the nuclear industry as a cladding material for nuclear reactors and loading nuclear fuel. From the perspective of safety and the economy, the recovery of zirconium from cladding waste at low temperatures is of strategic significance for nuclear energy. This work studied the electrochemical behavior of Zr(IV) and the separation of Zr metal in a low-temperature LiCl–KCl–CsCl molten salt system at 573 K (300 °C). Zr(IV) ion was reduced to metallic Zr through a two-step four-electron reaction process Zr(IV) → Zr(III) → Zr on the W electrode. The diffusion coefficients of Zr(IV) on the W electrode calculated by cyclic voltammetry and chronoamperometry were 5.805 × 10−5 cm2 s−1 and 2.861 × 10−5 cm2 s−1, respectively. Furthermore, the reaction activation energy of the Zr(III)/Zr(0) pair was measured to be 34.52 kJ mol−1 by the Tafel method. Then, the electrochemical recovery of Zr was accomplished on the W electrode by potentiostatic electrolysis at −2.0 V or galvanostatic electrolysis at 0.01 A, and two zirconium-containing products with the dendritic and flakes morphologies were obtained accordingly. This study provides a new low-temperature molten salt system for the reprocessing of zirconium cladding and shows the application potential of low-temperature molten salts LiCl–KCl–CsCl for spent fuel reprocessing.