Recovery of tungsten compounds from spent tungstophosphate catalyst using leaching, solvent extraction with phosphonium-based ionic liquids and precipitation

Igosawa, Tatsuki*; Matsumiya, Masahiko*; Sasaki, Yuji  

A novel hydrometallurgical process involving leaching, precipitation, solvent extraction using phosphonium-based ionic liquids (ILs), and crystallization stripping was developed. First, the spent catalyst was leached in distilled water. The leaching percentage of W(VI) was 99.9%. The phosphate ions were separated by precipitation using Fe(NO) as the precipitating agent. The separation percentage of phosphate was 90.8%. After the removal of phosphate, Alamine 336 and triethyl-npentylphosphonium bis(trifluoromethylaulfonyl)amide ([P][NTf]) were used as the extractant and diluent. The extraction percentage of W(VI) reached 94.6%. The stripping percentage of W(VI) reached 100% at pH8. Finally, crystallization proceeded at pH; 4.5, and the obtained precipitate was identified to be ammonium paratungstate.