Extraction Of Zirconium And Hafnium From Acidic Chloride Solution Using 2-ethyl Hexyl Phosphonic Acid Mono-2-ethyl Hexyl Ester (P₅₀₇)

In this disertation,the effects of extraction conditions on the equilibrium time, distribution ratio and separation factor of Zr and Hf from Zr(Hf)OCl₂ solution were investigated using 2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester(P₅₀₇)as extractant.The results showed that the extraction process is endothermic,and the equilibrium time is over 40 min.Some operation conditions can speed the extraction of Zr and Hf,however,the increase of extraction rate is still limited due to the slow formation process of extracted complex.The enthalpy changes of extraction reactions determined by slope method varied with the operation condition,indicating that the extraction mechanism was changeable in different test conditions.The molar ratios of metal ions to extractant in organic phase determined by isothermal method or saturation method were around at 3.6;1.The IR of extracted complex showed that Zr and Hf are extracted through the coordination of their hydroxyl polymer species with P₅₀₇.In most cases,Zr was extracted easier than Hf was,the reverse case only occured with low acidity and high Zr/P₅₀₇molar ratio.Therefore,the separation factor of Zr to Hf ranged from 1 to 4,and varied with extraction condition.With the increase of P₅₀₇concentration,β_Zr/Hfdecreased first and then increased,showing an minimal extremum at P₅₀₇concentration of 1 mol/L.The change ofβ_Zr/Hfcan also be explained by the extraction mechanism transition with extractant concentration.The extraction percentage of Zr and Hf also increased with the increase of phase ratio, however,the maximumβ_Zr/Hfwas observed when employing phase ratio of 1;1.