The Separation of Zirconium and Hafnium by Liquid-Liquid Partition of their Thiocyanates^†‡

The partition equilibria of zirconium and hafnium thiocyanates between water and methyl isobutyl ketone have been studied under various conditions. Since the system shows extremely marked deviations from Nernst's distribution law, the two elements cannot be prepared in a very pure state by a simple multi-stage partition. By the use of suitable additives and a new scheme of material flow, however, a continuous process using 23 mixer settlers has been developed, by means of which ZrO₂ containing less than 10 p.p.m. of HfO₂ and HfO₂ containing only 0.3% of ZrO₂ can be obtained from a zirconium-hafnium mixture (hafnium content: 1 to 2%).