Zirconium or Titanium is refined by Van Arkel refining.
Van Arkel method
Crude metal is heated with a suitable substance so that the pure metal present in it may be converted into a stable volatile compound leaving behind impurities. The compound so formed is then decomposed by heating to get the pure metal. This method is based on the thermal decomposition of metal components. The decomposition of a compound into different substances due to the supply of heat is called thermal decomposition.
When the impure titanium metal is heated with iodine at 2500 C, volatile titanium tetra-iodide is formed (TiI4). The impurities are left behind, as they do not react with iodine. The titanium tetra-iodide vapour is passed over a hot tungsten filament at 14000 C. The vapour is decomposed, and pure titanium is deposited on the filament and is removed. The iodine is reused.