Time-resolved laser-induced fluorescence of uranium(VI) hydroxo-complexes at different temperatures

Fluorescence measurements were performed at different temperatures to incre ase the resolving capabilities of time-resolved laser-induced fluorescence for uranium speciation. This spectroscopic technique was used to determine the fluorescence lifetimes of the uranyl ion and the species UO2OH+, (UO2), (OH)(2)(2+), and (UO2)(3) (OH)(5)(+) in 0.5 M NaClO4 solutions at different pH and total uranium concentration and in the temperature range from 10 to 60 degrees C, The temperature dependence of the lifetimes was found to fol low the Arrhenius law, and the activation energy of the process was determi ned for each species. The influence of temperature on the equilibrium const ants of the uranium hydroxo-complexes was also considered.