Characterisation of hydroxide complexes of uranium (VI) by time-resolved fluorescence spectroscopy
Deconvolution of composite fluorescence spectra and related decay curves for U(VI) in the pH range 0 to 5 and 9 to 11, at different total uranium concentrations, yielded decay times and individual fluorescence spectra for various hydroxo-complexes (UO(2))(m)(OH)(n)(2m-n), where (m,n) = (1,1); (1,3); (2,2); (3,5). Depending on emission wavelength, the fluorescence efficiency of (2,2) and (3,5) were found to be, respectively, 7 to 85, and 3 to 4 times higher than that of the uranyl ion, whereas the latter is about 3 times more fluorescent than the (1,1) complex. Thus relatively small concentrations of polynuclear species contribute appreciably to the overall fluorescence of aqueous U(VI) solutions. The fairly large difference between decay times and the high sensitivity of the equipment used made it possible to detect even small amounts of the hydroxo-complexes. In the alkaline pH range, 10 to 12, the (1,3) hydroxo-complex was found to predominate. In the presence of 0.05 M phosphate concentrations and in the same pH range, there was a pronounced change in the fluorescence spectrum indicating that the chemical speciation in the system had changed. This observation makes it necessary to revise the current equilibrium data for uranium (VI) phosphates complexes at high pH.
Bibliographic Reference: Article: Journal of the Chemical Society, Faraday Transactions (1995)
Record Number: 199511160 / Last updated on: 1995-08-23
Original language: en
Available languages: en