Removal of Hf(IV) Ions from Zr(IV) Ions in Sulfuric Acid Solution by Solvent Extraction with PC88A

The study aimed to remove Hf(IV) ions from Zr(IV) ions in sulfuric acid solution using PC88A, investigating the extraction and separation of high-concentration zirconium (Zr) and hafnium (Hf) in such systems. Key factors, including solution acidity and SO42− concentration, were examined. Results showed that acidity affected the size of Zr/Hf ion clusters, and PC88A exhibits a higher extraction preference for Hf(IV) over Zr(IV), achieving a separation factor (βHf/Zr) of 4.56 at 4 mol/L H+. Adding SO42− reduced its separation efficiency for Zr and Hf. Combined with slope analysis and FT-IR spectroscopy, Hf extraction by PC88A followed cation-exchange and solvation mechanisms, with 3 PC88A dimers consumed per Hf ion. Stripping experiments demonstrated that 1 mol/L sulfuric acid selectively stripped Zr from the loaded organic phase. Extraction and stripping equilibrium curves were constructed, confirming that 3 stages of Hf(IV) extraction from the solution and 4 stages of Zr(IV) stripping from the loaded organic phase are needed: 3 theoretical stages (O/A = 1) enabled complete Hf extraction, while 4 stages (A/O = 3:1) achieved full Zr stripping. This work provides a basis for efficient Zr-Hf separation using PC88A.