A novel bidentate diamide ligand DODQ for the separation of uranium and rare earth ions in nitric acid medium

• Published in: Hydrometallurgy 2024-06, Vol.226, p.106311, Article 106311
• Main Authors: Zhang, Miaomiao, Yang, Zhen, Su, Jianhui, Zhao, Heng, Xu, Chengjin, Sun, Jiahui, Liu, Xiaolei, Peng, Xiujing, Sun, Guoxin, Cui, Yu
• Format: Article
• Language: English
• Subjects: Bidentate diamide; Extraction separation; Rare earth elements; UO22
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2024.106311

High efficiency extractants play a necessary role in the selective removal of uranium from rare earth minerals. In this paper, a novel cyclic bidentate diamine extractant, 1, 4-dioctyl-1, 4-dihydroquinoxaline-2, 3-dione (DODQ), was synthesized, and the complexation and extraction of UO22+ in nitric acid medium were systematically studied. The results indicate that DODQ exhibits a unique combination of properties in removing UO22+, with an extraction capacity 132 times higher than that of DODPhOA (acyclic structure). Extraction isotherm experiments and slope analyses illustrate the formation of a 1:1 DODQ/UO22+ regime during the extraction process. Electrospray mass spectrometry, fluorescence spectroscopy, and X-ray crystal diffraction analyses further corroborated its stoichiometric properties. In addition, DODQ can remove UO22+ from rare earth solutions containing UO22+ with high selectivity. This study provides an alternative method to separate uranium from the leaching solution of rare earth ore and has a new understanding of the coordination and complexing behavior of UO22+ with bidentate oxygen-containing ligands. Due to the design of the bidentate oxygen of the extractant structure itself, which is orthogonal to the uranyl ion, DODQ has a good extraction ability and selectivity towards UO22+, and achieves the separation of UO22+ and Ln3+. [Display omitted] •A new and effective extractant for UO22+ is synthesized and characterized.•Fixing the orientation of carbonyl groups (C=O) onto the extractant structure.•The extraction capacity of DODQ was determined to be 132 times higher.•The extraction ability of 0.1 mol/L DODQ is better than that of 0.1 mol/L TBP.•DODQ can selectively concentrate UO22+ in a rare earth ore simulation solution.