New Process for Zirconium and Hafnium Separation

Abstract

The separation of hafnium and zirconium, required for nuclear use of zirconium, is generally performed by liquid-liquid extraction in organic solvents. The paper describes a new process based on extractive distillation of zirconium chloride (ZrCl4) and hafnium chloride (HfCl4) in a solvent made of molten potassium chloride-aluminum chloride (KCl-AlCl3) mixture above 350°C at atmospheric pressure. The corresponding process is now in full-scale industrial production.

Selective extraction of Hf(IV) over Zr(IV) from aqueous H2SO4 solutions by solvent extraction with acidic organophosphorous based extractants

“…The difficulties encountered are mainly due to the chemical similarities of the respective elements. Among the various alternatives, such as multiple crystallization, extractive distillation and solvent extraction, the crystallization process is the simplest to recover both Zr and Hf, but the method is only of interest in batch operation . Solvent extraction is regarded as a promising method to separate metallic elements …”

Nuclear fuel assembly design and fabrication

“…The impurities remaining in nuclear grade zirconium after the hafnium extraction process are given in Table 9.3 (Moulin et al , 1984).…”

Nuclear-grade zirconium prepared by combining combustion synthesis with molten-salt electrorefining technique

“…Because the two metals are so similar, complicated and expensive separation methods are needed to remove hafnium impurities. There are three established technologies for separation of zirconium and hafnium: multiple crystallization of potassium zirconium fluoride, solvent extraction processes, and extractive distillation [2][3][4]. In the multiple crystallization process, sodium zirconate (Na 2 ZrO 3 ), obtained by caustic soda fusion with zircon sand, is dissolved in concentrated nitric acid.…”

“…The hafnium is preferentially extracted as hafnyl thiocyanate, using methyl isobutyl ketone (MIBK). The remaining aqueous solution is reacted with sulfuric acid to form pentazirconyl sulfate, which is precipitated by adjusting the pH with ammonium hydroxide [4,6]. The zirconium hydroxide obtained is dried and calcinated to give hafnium-free ZrO 2 .…”

“…The sophisticated technologies and energy consumption required for the extractive distillation process have led to a search for new zirconium and hafnium separation processes [6]. The development of an effective separation method still attracts the attention of many separation chemists; solvent extraction [4,7], solid/liquid extraction [8][9][10][11], and alternative processes [12][13][14][15][16] have recently been proposed.…”