The influence of the treatment of Zr(IV) and Hf(IV) sulfate solution on the ion-exchange purifying of zirconium from hafnium on Diphonix® resin

• Treating stock solutions proved to be a very important step in Hf and Zr separation.
• The best separation was achieved using a fluoride complex creation intermediate stage.
• This increases the separation efficiency of ten times the usually prepared solution.
• Temperature was found to be a crucial parameter for feed solution preparation stages.

The tendency of Zr(IV) and Hf(IV) to form polynuclear species (especially mixed Zr–O–Hf complexes) in aqueous solutions is, besides their almost identical chemical properties, one of the main obstacles in their separation. Therefore, finding a suitable way for the aforementioned complexes to decompose may play a crucial role in efficiently purifying zirconium from hafnium. The best purifying efficiency on Diphonix® resin was obtained with a zirconium sulfate solution prepared with the intermediate stage of fluoride complexes creation. This permits the collection of the purest fraction of the zirconium sulfate solution, which has a hafnium content ten times lower than in the case of typically prepared solutions.