Anodic behaviour of Cu, Zr and Cu–Zr alloy in molten LiCl–KCl eutectic

Abstract

The anodic dissolution behaviours of Cu, Zr and Cu–Zr alloy were analysed in LiCl–KCl at 500°C by anode polarization curve and potentiostatic polarization curve. The results show that the initial and fast-dissolving potentials of Cu are −0.50 and −0.29 V, and Zr are −1.0 and −0.88 V, respectively. But, in the Cu–Zr alloy, the initial and fast-dissolving potentials of Cu are −0.52 and −0.41 V, and Zr are −0.96 and −0.92 V, respectively. The potentials satisfy the selection dissolution principle that Zr in the alloy dissolves first, while Cu is left in the anode and is not oxidized. The passivation phenomenon of Zr is observed in the quick dissolution of Zr, while it is not observed in the Cu–Zr alloy. Moreover, from the above anodic dissolution results, potentiostatic electrolysis of Cu–Zr alloy was carried out at −0.8 V for 40 min, and the anodic dissolution mechanism and kinetics of Zr in Cu–Zr alloy were also discussed. In the initial stage, Zr dissolves as Zr4+ ions from the alloy surface and enters into the molten salt, leaving a Cu layer called ‘dissolving layer’ on the surface of the alloy. After that, another layer between the matrix and ‘dissolving layer’ called ‘diffusion–dissolution layer’ appears. Zr diffuses in the alloy matrix and dissolves as Zr4+ ions on the surface of the ‘diffusion–dissolution layer’ continuously, and Zr4+ ions diffuse through the ‘dissolving layer’ and enter into the molten salt finally. In addition, the factors affecting the dissolution of Cu–Zr alloy, such as time and potential, were also investigated. The dissolution loss increases with the increasing dissolution potential and time, while the dissolution rate increases with the increasing dissolution potential and declines with the prolonging dissolution time.

Optical monitoring of the anodic dissolution of zirconium and the agglomeration of potassium hexachlorozirconate during transpassive dissolution in molten LiCl–KCl salt

“…One promising methodology for recycling spent fuel Zralloy cladding is an electrometallurgical process that uses molten LiCl-KCl salt as a medium. [7][8][9][10][11][12][13][14][15][16][17][18][19] For such a process, the direct anodic dissolution of Zr-alloy cladding is the most straightforward strategy for administering Zr reactants into molten LiCl-KCl salts. 8,16 Since Zr-alloy cladding is generally composed of 97% or more of Zr; 8 it is essential to rigorously understand the anodic dissolution behavior of Zr in molten LiCl-KCl salt.…”

“…In addition, our group 24 reported that the dissolution of Zr is accelerated rapidly at a more positive potential than the passivation potential proposed in previous publications. Cai et al 12 argued that the rapid increase in the dissolution current might be related to the transpassivation of Zr.…”

Anodic dissolution behavior of Zr‐Dy alloy in LiCl‐KCl molten salt

“…Even after most of the U was dissolved, the noble metals still remained in the anodic residue while Zr metal remained in the anode. Cai et al 15 explored Zr, Cu and Cu‐Zr alloy dissolution at anode in LiCl‐KCl melts, and the dissolution behavior, mechanism and kinetic data were investigated. Their results indicated that Zr was dissolved firstly in Cu‐Zr alloy to form Zr 4+ , while Cu was left in the alloy and not oxidized.…”

In situelectrochemical investigation of the reaction progress between Zr and a CuCl–SnCl2mixture in a LiCl–KCl molten salt

“…Therefore, due to its economic and environmental value, it is highly necessary to recycle zirconium present in residual and waste materials. 4 Among the methods available for recycling, much attention has been paid to electrochemical renement of zirconium in molten salts. Commonly, the electrorening of Zr occurs in alkali chloride, uoride, or chloride-uoride mixed fused melts.…”

“…Therefore, due to its economic and environmental value, it is highly necessary to recycle zirconium present in residual and waste materials. 4 …”