Spectroscopic study of Cm(III) sorption onto gamma-alumina

The surface sorption of Cm(III) onto aqueous suspensions of alumina is inve stigated by time-resolved laser fluorescence spectroscopy (TRLFS). The expe riment is performed under an Ar atmosphere at an ionic strength of 0.1 M Na ClO4. The pH is varied between 2 and 10 and the metal ion concentration bet ween 2.7 x 10(-8) and 4.5 x 10(-5) mol/L. With increasing pH, two Cm(III)-a lumina surface species are identified which are attributed to drop Al-O-Cm2 +(H2O)(5) and drop Al-O-Cm+(OH)(H2O)(4). The two curium-alumina surface com plexes are characterized by their emission spectra (peak maxima at 601.2 nm and 603.3 nm, respectively) and fluorescence emission lifetime (both 110 m us). In the concentration range investigated, the surface complex formation is not dependent on the metal ion concentration but only on the pH. Additi onally, the concentration ratio of the two surface species is found to be i ndependent of the metal ion concentration. No spectroscopic evidence for th e presence of "strong" and "weak" sites can be found at different surface c overages. (C) 2001 Academic Press.