SOLVENT-EXTRACTION OF HF(IV) FROM MIXED ELECTROLYTE-SOLUTIONS INTO DI-2-ETHYLHEXYLPHOSPHORIC ACID (HDEHP)

Extraction of hafnium(IV) from aqueous sulfuric and sulfuric-nitric acid solutions into di-2-ethylhexylphosphoric acid (HDEHP) in xylene has been investigated. The Hf(IV) species extracted from 5M sulfuric acid was found to be HfY2(HY2)2 where Y and HY2 represent the anions of monomeric HY and dimeric H2Y2 forms of HDEHP, repectively. In the presence of nitrate ion the species extracted are found to be Hf(NO3)Y(HY2)2 and Hf(NO3)2(HY2)2. But when the aqueous phase is 3.0M HNO3 + 2.5M H2SO4 only one species, Hf(NO3)2(HY2)2 was extrated. No synergism was observed from 5M H2SO4 by HDEHP with the addition of thenoyltrifluroacetone (HTTA).