A STUDY OF U(VI) HYDROLYSIS AND CARBONATE COMPLEXATION BY TIME-RESOLVED LASER-INDUCED FLUORESCENCE SPECTROSCOPY (TRLFS)

Chemical species of U(VI) in 0.1 M perchlorate solutions in equilibrium with 0.03% CO2 Partial pressure were investigated by time-resolved laser-induced fluorescence spectroscopy. The emission spectra of U(VI) solutions (pH = 3.8 to 7.0) in solid-liquid equilibrium with schoepite UO3 . 2H2O were interpreted by the summation of the emission spectra of the individual components, UO22+(aq), (UO2)2(OH)22+(aq), (UO2)3(OH)5+(aq) and UO2CO3(aq). Numerical evaluation of the emission spectra using the single component of the species gave a satisfactory agreement with the distribution of the species calculated from the formation constants of U(VI)-hydroxides and -carbonate complexes. Emission spectra of the higher carbonate species UO2(CO3)22- and UO2(CO3)34- could not be observed.