Purification process Zirconium-Hafnium separation

The purification step of hafnium removal from zirconium is carried out under an inert atmosphere (preferably argon), by using a CuCl2-bearing molten salt with the following reaction  

With this reaction, hafnium in the molten metal is preferably transferred to the molten salt phase, and consequently CUCI2 is reduced to metallic copper dissolving into the Zr-containing Cu-based low melting alloy. The kinetics of the interfacial reactions between molten metal and molten salt is usually very fast. The equilibrium composition for both phases can be established in laboratory experiments. Thermodynamic prediction of the reaction system gives very encouraging results for this separation process. 

---

Although the solvent purification process is adequate for the production of say reactor-grade zirconium, it is possible to modify it so that pure hafnium may also be obtained. Distribution data are available for various solutions containing thiocyanate, sulphate and chloride from which it is possible, for example, to deduce that both hafnium and zirconium will extract into hexone provided the aqueous phase has a high thiocyanate concentration and a low chloride concentration. The zirconium may then be selectively backwashed in a second extractor using say an aqueous phase of high thiocyanate concentration and moderate sulphate concentration, where the separation factor of the system is high. The hafnium can then... 

A new and more compact process for the production of pure zirconium with a sufficiently low content of hafnium has been developed by Xiao and Sandwijk [22]. The separation process aims to improve Megy s process [20], in particular by providing a purification process with a higher thermodynamic separation potential at... 

---