Effect of humic acid on the sorption of Cm(III) ontoγ-Al2O3studied by the time-resolved laser fluorescence spectroscopy
| Autor: | Thomas Rabung, Horst Geckeis, R. Klenze, Thomas Fanghänel, Xu-cong Wang, Petra J. Panak |
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| Rok vydání: | 2004 |
| Předmět: | |
| Zdroj: | Radiochimica Acta. 92:691-695 |
| ISSN: | 2193-3405 0033-8230 |
| DOI: | 10.1524/ract.92.9.691.54982 |
| Popis: | SummarySorption of Cm(III) ontoγ-alumina coated with humic acid (HA) is studied by the Time Resolved Laser Fluorescence Spectroscopy (TRLFS). The experiments are performed at 0.1 M NaClO4, 0.44 g/Lγ-Al2O3, 10 mg/L HA and at a metal ion concentration of 2×10-7mol/L. At the investigated pH range (4 to 10) HA is completely sorbed to γ-Al2O3. The excitation spectrum of Cm(III) bound to HA/γ-Al2O3in the wavelength range 370-400 nm exhibits broad flat bands very different from those obtained for the Cm(III) aquo ion and the Cm(III)-γ-Al2O3surface complex, respectively. The spectrum, lacking distinctive structure due to intramolecular energy transfer processes, points to the predominant binding of the Cm(III) to surface-bound HA. TRLFS experiments performed at two different excitation wavelengths (λex=355 and 396.6 nm) allow for a differentiation of humic-bound and non-humic-bound Cm(III). Differences in fluorescence spectra obtained at the different excitation wavelengths are found at pHex=355 nm). At pH≥7, the fluorescence spectra obtained by indirect and direct excitation become congruent and again point to the existence of only humic-bound Cm(III) species. Comparison of peak maxima and fluorescence lifetimes for Cm(III)-HA and Cm(III)-HA/γ-Al2O3, however, reveal differences. The results clearly indicate a contribution of theγ-Al2O3surface to the Cm(III) binding and, thus, suggest the formation of ternary complexes such as >Al-O-Cm(III)(HA). |
| Databáze: | OpenAIRE |
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