Spectroscopic studies on uranyl complexes with tri-n-butyl phosphate (TBP) in ionic liquids

The complexes formed from uranyl salts and tri-n-butyl phosphate (TBP) in ionic liquids (ILs) were studied by spectroscopic methods. [UO2(TBP)(4)](2+) is formed from UO2(ClO4)(2)center dot xH(2)O with excess of TBP in ILs. The coordination number of uranyl in [UO2(TBP)(4)](2+) is determined as 4 by ATR-FTIR study. In [Bmim][NTf2], though TBP cannot replace the NO3- coordinated to uranyl, TBP/[Bmim][NTf2] can extract "nitrate-free" uranyl complex from diluted HNO3 medium and the extracted complex is converted into [UO2(TBP)(4)](2+) after drying. The formation of [UO2(TBP)(4)](2+) provides spectroscopic evidence for the cation-exchange mechanism of uranyl extraction by TBP/[Bmim][NTf2] from diluted HNO3 medium.National Natural Science Foundation of China [91026011, 11575010]SCI(E)ARTICLEtwchu@pku.edu.cn31071-107930