Solvent Extractive Separation of Zirconium and Hafnium from Hydrochloric Acid Solutions by Organophosphorous Extractants and Their Mixtures with Other Types of Extractants

Breaking through the Separation Barrier of Zr(IV) and Hf(IV): Magical Effect of the Bisamide Ligand

The fundamental safety improvement of the nuclear industry depends on two important elements: Zr(IV) and Hf(IV). However, the elementary knowledge is that separation processes of the two are difficult, so there are few existing methods to meet the requirement. Furthermore, the process is highly contaminated. The development of green and efficient ligands for the separation of Zr(IV) and Hf(IV) is beneficial to the stable development of the nuclear industry. A bisamide ligand D001 was reported for the extraction and separation of Zr(IV) and Hf(IV). D001 utilizes an anionic association mechanism to extract Zr(IV) and Hf(IV) by coordinating amide groups with metals to form complexes H₂ZrCl₆·2 D001 and H₂HfCl₆·2 D001. Using quantum chemical calculations, we illuminate the extraction mechanism of bisamide ligands and the reasons for their better coordination ability than monoamide ligands and carboxylic acid ligands. A process of bisamide extraction and separation of Zr(IV) and Hf(IV) was established, and the thermodynamic parameters of the process were investigated.

Solvent extraction separation of zirconium and hafnium from nitric acid solutions using mixture of Cyanex-272 and TBP

A solvent extraction method has been employed to extract and separate zirconium and hafnium from the nitric acid medium using Cyanex-272 and its mixture with TBP in kerosene. The effects of the experimental parameters such as contact time between phases, aging time, nitric acid concentration, Cyanex-272 and TBP concentration on the metals separation, and various stripping agents on the metals back extraction from the loaded organic phase have been investigated. The maximum separation factor of 16 was obtained in the single extraction system with 1% (v/v) Cyanex-272 from 2.5 M HNO3 solution. The combination of Cyanex-272 with TBP exhibited a significant synergistic effect for Zr extraction and the antagonistic effect for Hf extraction. The proposed novel synergistic mixture consisting of 0.5% (v/v) Cyanex-272 and 20% (v/v) TBP in kerosene offered the maximum separation factor of 99.7 from 2.5 M HNO3 solution. By applying a slope method, the extracted zirconium species were proposed to be ZrO(NO3)2·2Cyanex272·2TBP in the organic phase. Among the investigated stripping agents, 4 M H2SO4 solution showed the best efficiency for the stripping of zirconium and hafnium from the loaded mixture of Cyanex-272 and TBP with separation factor of 10.1.