Aluminum complexes thiocyanates

The zirconium tetrachloride product must then be purified before reduction to metal. In particular, hafnium must be removed to less than 100 ppm Hf Zr because of the high neutron absorption cross-section it exhibits, and phosphorus and aluminum must be removed to even lower specifications due to their deleterious metallurgical impact on the final zirconium alloys. The tetrachloride product is first dissolved in water under carefully controlled conditions to produce an acidic ZrOCl2 solution. This solution is complexed with ammonium thiocyanate, and contacted with methyl isobutyl ketone (MIBK) solvent in a series of solvent extraction columns. Advantage is taken of the relative solubilities of Zr, Hf, and Fe thiocyanate complexes to accomplish a high degree of separation of hafnium and iron from the zirconium. 

Twenty per cent TBF dissolved In kerosene was used as extractant. The partition coefficient, increases with Increased TBF concentration. Increases with increased pH, and decreases with increased sulfate concentration. Vanadium and Iron (ill) are appreciably extracted by TBP from thiocyanate solutions. Copper, titanium, cobalt are weakly extracted. Iron (ll), cadmium, molybdenum, magnesium and aluminum are essentially not extracted. Phosphate Ion may cause the precipitation of uranium or complex formation when present in large amounts. Okada, et al. report the extraction of uranium by TBP, mesityl oxide, and methyl ethyl ketone from phosphoric acid solutions having 20 times as much ammonium thiocyanate as uranium. 

---