SOLVENT EXTRACTION OF HAFNIUM(4) .6. EXTRACTIRION OF HF(4) BY SOME DIALKYLPHOSPHORIC ACIDS FROM CHLORIDE AND NITRATE MEDIA

The distribution of 175+181Hf(IV) between aqueous hydrochloric or nitric acid and (i) a solution of dibutylphosphoric acid in benzene and chloroform, (ii) di-n-amylphosphoric acid in toluene and (iii) diethylhexyl-and di-n-octylphosphoric acids in n-octane has been studied. In the range of concentrations of Hf used (up to 2 × 10-6M), Hf is extracted from a hydrochloric acid medium up to CHCI of 3·5 M predominantly as HfClA3(HA)2, where HA is the dialkylphosphoric acid. In a medium of nitric acid at CHNO3 ≥ 1·5 M, or in one of hydrochloric acid at CHCI ≥ 4·5 M, the initial ion-exchange reaction mechanism is replaced by an addition type of reaction with the formation of extractable complexes of HfX4(HA)y, where X = NO3, Cl. At higher concentrations of HNO3, an extractable HNO3·HA complex is formed which results in a decrease in the distribution ratio of Hf. © 1968.