Solvent extraction of iron, zirconium and hafnium with tertiary aliphatic amines

The equilibrium reaction for a:line extraction has boon used to derive on equation relatin7, the distribution ratio of a staple anion or an anionic notal complex to the activities of the species takin: part in the equilibrium.This equation has been used to derive expressions for the slopes of plots of loc Dre arfainst Icy' concentration.The distribution ratios of iron (III) between aqueous nitrate-thiccyanato media of pH 2 and.sUutdans of tri-iso-nonylaminc in benzene, and of hafnium (IV) between acidic (0.5-2M) sulphate-chloride media and tri-n-octylamine in benzene, have been measured usinF radioactive tracers.The distribution of the complexinz anions, thiocyanate and bisulphate was also, studied.Fractions of the various aqueous species present were calculated from published data on their respective stability constants.Results of thiocyanate extraction were in Toed asreemont with the extraction equation, whilst those for bisulphate distribution also fitted statistically despite larf, :e expeririontal scatter.The distribution ratio of iron was found to decrease with increasing iron concentration.This could be explained in terns of the formation of a polymeric iron species Fe2(Sal)6.The formation constant of this species was calculated.The distribution of hafnium was in 7ood =eement with the extraction eauatian.The value of the extraction equilibrium constant was calculated for iron (III) thiocycnatel 'hafnium sulphate, thiocyanate, and bisulphate from the exoreinental results and for zirconium sulphate fro-1athe results in the literature.