1. It can be made from magnesium reduction of hafnium tetrachloride or thermal decomposition of hafnium tetrachloride. HFCl4 and K2HFF6 can also be used as raw materials. In NaCl-KCl-HFCl4 or K2HFF6 melt electrolytic preparation, the process is similar to zirconium electrolytic preparation.
2. Hafnium and zirconium coexist, there is no separate hafnium raw material. The raw material of hafnium is coarse hafnium oxide separated from zirconium manufacturing process. The hafnium oxide is extracted by means of an ion exchange resin and the metal hafnium is subsequently produced from this hafnium oxide in the same way as zirconium.
3. It can be prepared by reduction of hafnium tetrachloride (HfCl4) and sodium by co-heating.
4. The earliest separation methods of zirconium and hafnium are fractionated crystallization of fluorine complex salts and fractionated precipitation of phosphate. These methods are cumbersome to operate and are limited to laboratory use. New techniques for separation of zirconium and hafnium, such as fractional distillation, solvent extraction, ion exchange and fractional adsorption, have emerged one after another, among which solvent extraction has more practical value. Two commonly used separation systems are thiocyanate-isohexanone system and tributyl phosphate - nitric acid system. All the products obtained by the above methods are hafnium hydroxide. Pure hafnium oxide can be obtained by calcination. High purity hafnium can be obtained by ion exchange.
