Extraction of Uranium and Thorium from Nitric Acid Solution by TODGA in Ionic Liquids

• Published in: Separation science and technology 2014-08, Vol.49 (12), p.1895-1902
• Main Authors: Zhang, Youwen, Liu, Ziyi, Fan, Fuyou, Zhu, Lun, Shen, Yinglin
• Format: Article
• Language: English
• Subjects: extraction; imidazolium-based ionic liquid; thorium(Th; TODGA; uranium(UO
• ISSN: 0149-6395; 1520-5754
• DOI: 10.1080/01496395.2014.903279

Extraction of uranium (UO 2 2+ ) and thorium (Th 4+ ) from a nitric acid solution into an imidazolium-type ionic liquids (ILs) of 1-alkyl-3-methylimidazolium hexafluorophosphate ([C n mim][PF 6 ], n = 6 or 8) was carried out using N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as an extractant. It was found that the extraction efficiencies of UO 2 2+ and Th 4+ ions are higher in comparison with that done in n-dodecane. The extraction mechanism was deduced by the slope analysis and extraction experiment. Transfer of both ions is assumed to proceed predominantly through the neutral solvation mechanism from nitric acid solution into ILs. The UO 2 2+ ion forms a 1:2 complex with TODGA in ILs at lower acidity, and a 1:1 complex in ILs and in n-dodecane at higher acidity. The Th 4+ ion forms a 1:2 complex with TODGA in C 6 mimPF 6 IL or a 1:1 complex in C 8 mimPF 6 IL at lower acidity and a 1:1 complex in both ILs, and n-dodecane at higher acidity. Stripping studies were conducted using sodium salt of EDTA as a stripping ligand. The thermodynamics of extracting UO 2 2+ ions and Th 4+ ions from a 3 M HNO 3 solution was also studied. The results indicated that the extraction reactions are spontaneous and go through an exothermic process.