Extraction of uranium (VI) by 1.1 M tri- n-butylphosphate/ionic liquid and the feasibility of recovery by direct electrodeposition from organic phase

• Published in: Journal of alloys and compounds 2008-01, Vol.448 (1), p.104-108
• Main Authors: Giridhar, P., Venkatesan, K.A., Subramaniam, S., Srinivasan, T.G., Vasudeva Rao, P.R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical engineering; Cyclic voltammetry; Electrodeposition; Exact sciences and technology; Ionic liquid; Liquid-liquid extraction; Solvent extraction; Uranium
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2007.03.115

The diluent characteristics and the wide electrochemical window of the room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide (bmimNTf 2), has been exploited for the extraction of uranium (VI) from nitric acid medium using 1.1 M solution of tri- n-butylphosphate (TBP) in bmimNTf 2, followed by direct electrodeposition as uranium oxide from organic phase. The extraction of uranium (VI) with 1.1 M TBP/bmimNTf 2 has been studied as a function of nitric acid concentration and the distribution ratios were compared with those obtained with 1.1 M TBP/ n-dodecane and 1.1 M TBP/bmimPF 6. The amount of water and nitric acid co-extracted into the organic phase was measured. The electrochemical behavior of a solution of uranyl nitrate in 1.1 M TBP/bmimNTf 2 on a glassy carbon working electrode was studied using cyclic voltammetry. The voltammogram consists of a single reduction wave occurring at a peak potential of −1.3 V (versus Pd quasi-reference electrode) due to the reduction of U(VI) and a broad oxidation wave occuring at 0.56 V. Controlled potential electrolysis of uranium (VI) extracted 1.1 M TBP/bmimNTf 2 phase gave a black deposit of uranium (IV) oxide, which on heating or exposure in air leads to a mixture of uranium (IV) and uranium (VI) oxides. The lean organic phase can be recycled after electrodeposition.