Method for refining and separating a metal selected from the group consisting of titanium, zirconium, cerium, hafnium and thorium

Titanium, zirconium, cerium, hafnium or thorium are refined, or separated, by heating the metal with sufficient carbon monoxide to form the compound M(CO)7, where M is the metal, distilling off the M(CO)7 formed, and dissociating the distilled M(CO)7 by heating to precipitate the metal and release CO. Finely divided titanium is charged through 10 into pressure vessel 11 and is agitated by stirrer 18, while being heated to 300-800 DEG C. by burners 12. Excess CO enters at 13 and the pressure in 11 should be 2-10 atmospheres, which may be maintained by CO alone or by addition of inert gas, e.g. helium or argon. Preferred conditions are 400 DEG C. at 4-8 atmospheres. Where the reaction speed has fallen appreciably, as indicated by CO absorption, the temperature is raised 50-100 DEG C. to distil the Ti(CO)7 in to the precipitation vessel 16 which is isolated by valve 19. The temperature is raised a further 50-100 DEG C. by gas burner 24, when titanium is deposited. The CO is purged through 22 by inert gas, e.g. helium or argon, entering at 21, and these purged gases may be led through additional precipitation chamber or chambers, to effect complete recovery of titanium, and the CO gases may be recycled to the pressure vessel. To effect separation of metls, e.g. zirconium and hafnium, the mixed metals are both converted to the carbonyls, then Zr(CO)7 is distilled first into one precipitation chamber, and Hf(CO)7 is distilled at a higher temperature to a separate precipitation chamber. The two carbonyls are decomposed by further heating to precipitate the pure metals. Alternatively, the Zr(CO)7 and Hf(CO)7 may be distilled together into a precipitation vessel in which the temperature is controlled to dissociate only the Zr(CO)7, and the Hf(CO)7 is purged to another vessel with the CO and inert gas for dissociation.