Separation of hafnium from zirconium in HNO3 solution by solvent extraction with Cyanex572

Extraction and separation of hafnium (Hf) from zirconium (Zr) in HNO3 solution were carried out with Cyanex572 as extractant. Hf could be selectively extracted with an optimized extraction rate of 76.8%, and the separation factor between Hf and Zr could reach up to 15.7 when the concentration of Zr(IV), Hf(IV), H+, NO3− and (NH4)2SO4 in aqueous phase were fixed at 110 g/L, 3.0 g/L, 2.6 M, 1.8 M and 0.8 M, respectively. The stoichiometry and coordination structure of the extracted complex for Hf was investigated by slope analysis, Fourier transform infrared (FT-IR) spectrometry and nuclear magnetic resonance (NMR) spectrometry. It was found that HfO2+ in nitric acid medium could be extracted into the organic phase through two routes. The dominant route was via a cation-exchange mechanism, according to 2HfO2+aq + H2A2 org + 2NO3̄ aq↔ (HfO2+)2·(NO3̄)2·A2 org + 2H+aq. Meanwhile, the subordinate route was coordinate with PO in Cyanex572 extractant. Therefore, it is possible to developing an effective solvent extraction system to separate Hf from Zr by utilizing Cyanex572.