SOLVENT EXTRACTION OF HAFNIUM(4) .8. EXTRACTION OF HF(4) BY SOME DIALKYLPHOSPHORIC ACIDS FROM BROMIDE IODIDE AND SULPHATE MEDIA

The distribution of 175+181Hf(IV) between aqueous hydrobromic, hydroiodic or sulphuric acid and a solution of dibutyl,-di-n-amyl-, diethylhexyl- and di-n-octylphosphoric acids in various organic solvents has been studied. In moderately acidic solutions of halogenacids, Hf is extracted as HfXA3(HA)x, where HA is the dialkylphosphoric acid and X is the halogen. In strong acidic solutions, the originally ion-exchange extraction mechanism is replaced by an addition type of reaction with the formation of extractable complexes of the composition HfX4(HA)y. In sulphate solutions, with the exception of dioctylphosphoric acid, complexes of the HfA4(HA)y type are extracted in moderately acidic medium and in strong acidic medium the extraction mechanism is again changed and solvated sulphate complexes of Hf are formed. © 1969.