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

Abstract

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.