Electrochemical Behavior of U(VI) in Imidazolium Ionic Liquid Medium Containing Tri‐n‐butyl Phosphate and Chloride Ion and Spectroscopic Characterization of Uranyl Species

• Published in: ChemistrySelect (Weinheim) 2017-09, Vol.2 (27), p.8706-8715
• Main Authors: Krishna, Gajula Murali, Suneesh, Asokan Sudha, Kumaresan, Radhakrishnan, Venkatesan, Konda Athmaram, Antony, Malpan Pailo
• Format: Article
• Language: English
• Subjects: Diffusion coefficient; Room temperature ionic liquid; Spectroscopy; Uranium; Voltammetry
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.201701139

The electrochemical behaviour of UO2(NO3)2in a solution of tri‐n‐butyl phosphate (TBP) present in 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (C4mimNTf2) ionic liquid was studied in the presence of chloride ion, to understand the decomplexation behaviour of uranyl ion (UO22+)from TBP coordination, and to examine the possibility of underpotential reduction of UO22+. The mole ratio of U : NO3 : TBP : Cl in ionic liquid solution was varied from 1 : 2 : 2 : 0to 1 : 2 : 2 : 6 in the study. The cyclic voltammogram of UO2(NO3)2 present in TBP/C4mimNTf2, was compared with the voltammograms obtained in the presence of 1‐butyl‐3‐methylimidazolium chloride (C4mimCl). The current density of UO22+ reduction increased with increase in the chloride content of ionic liquid phase, which was attributed to the formation of chloro complexes of uranium (VI), and these chloro complexes were found to undergo facile and favourable reduction at the working electrode. The diffusion coefficient of uranylspecies was determined at various concentrations of chloride ion and the nature of uranylspecies diffusing at the working electrode at various mole ratios of U : NO3 : TBP : Cl was characterized by UV–Visible, ATR‐FTIR and Raman spectroscopy. The voltammetric behaviour of UO2(NO3)2 in the presence of a ligand, tri‐butyl phosphate, was very complicated. The electrochemical behaviour of uranyl ion was tamed by adding chloride based ionic liquid. The diffusion coefficient of uranyl species was determined at various concentrations of chloride ion and the nature of uranyl species was characterized by UV–Visible, ATR‐FTIR and Raman spectroscopy.