Highly Efficient Separation of Hafnium Over Zirconium via a Newly Designed MIBK-HSCN-Glycine Extraction System

Zirconium (Zr) and hafnium (Hf) are pivotal in the nuclear industry. This study introduces a novel extraction system utilizing Methyl isobutyl ketone (MIBK), thiocyanic acid (HSCN), and glycine to enhance the separation of Zr and Hf. Under optimized extraction conditions, the separation coefficient of Hf to Zr reaches 8.58, nearly double that of the traditional MIBK – HSCN system. Monitoring the flow direction of glycine reveals that it does not enter the organic phase; rather, glycine predominantly improves the separation coefficient by modulating the complexation of Zr and Hf in the aqueous phase, as evidenced by FTIR, Raman spectroscopy, and NMR analysis. The aqueous phase spectrum shows that glycine forms a complex with metal ions in the aqueous medium. The complexation form of Hf evolves from Hf(OH)(SCN)3 to Hf(OH)2(SCN)2 upon the addition of glycine, while the complexation of Zr remains unchanged, resulting in an increase in the ratio of KHf to KZr from 1.4 to 18.2. Following this, the scrubbing process is systematically analyzed, yielding a separation coefficient of 10.0. During the cleaning process, as the acidity of the washing solution increases, SCN− in the oil phase becomes more difficult to enter the aqueous phase. Finally, a process comprising six theoretical stages of extraction coupled with six theoretical stages of scrubbing is designed based on a split-flow extraction model, achieving a purity and product yield of Hf exceeding 99%.