Equilibrium of zirconium and hafnium in the process of extraction with TBP in nitric medium – Influence in the Zr/Hf separation

The stoichiometric relation of zirconium and hafnium in the extraction process with tributyl phosphate (TBP) in nitric acid media was investigated. The present work investigates the influence of the process variables on the distribution (D) and separation of zirconium and hafnium by (TBP) from nitric acid solutions. Acidity is the variable that most influences the separation of zirconium and hafnium under the conditions evaluated. The equations proposed for the equilibrium and stoichiometric coefficients were: for zirconium (Zr(OH)4 + 4HNO3 ⇆ Zr(NO3)4 + H2O and Zr(NO3)4 + 2TBP ⇆ Zr(NO3)4(TBP)2); and for hafnium ([Hf(H2O)6]4+ + 4NO3− ⇆ Hf(NO3)4 + 6H2O and Hf(NO3)4 + 2TBP ⇆ Zr(NO3)4(TBP)2).