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Published on: August 12, 2019
Spectroscopic identification of ternary Cm-carbonate surface complexes
M Marques Fernandes1, T Stumpf, B Baeyens
1Laboratory for Waste Management, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland. maria.marques@psi.ch
Environmental Science & Technology
|January 7, 2010
Summary
Dissolved carbon dioxide (CO2) influences trivalent curium (Cm) sorption on minerals. Spectroscopic evidence shows Cm(III)-carbonate surface complexes form at the mineral-water interface.
Area of Science:
- Environmental Science
- Geochemistry
- Radiochemistry
Background:
- Understanding radionuclide behavior in the environment is crucial for waste management.
- Trivalent curium (Cm) is a key actinide relevant to nuclear waste disposal.
- Sorption processes at mineral-water interfaces significantly affect radionuclide mobility.
Purpose of the Study:
- To investigate the effect of dissolved carbon dioxide (CO2) on the sorption of trivalent curium (Cm) onto alumina (gamma-Al2O3) and kaolinite.
- To provide spectroscopic evidence for the formation of Cm(III)-carbonate surface complexes.
Main Methods:
- Time Resolved Laser Fluorescence Spectroscopy (TRLFS) was employed to study Cm sorption.
- Measurements were conducted at low temperatures (T < 20 K) on Cm-loaded mineral wet pastes.
- Spectra were compared between samples with and without carbonate to identify changes.
Main Results:
- The presence of carbonate caused a red-shift in excitation and emission spectra of Cm.
- Fluorescence lifetimes of Cm increased in the presence of carbonate, indicating complex formation.
- Biexponential decay of fluorescence lifetime suggests at least two distinct Cm(III)-carbonate species.
Conclusions:
- Dissolved CO2, via carbonate complexation, significantly influences Cm sorption on alumina and kaolinite.
- The study provides the first spectroscopic evidence for ternary Cm(III)-carbonate surface complex formation.
- These findings are vital for predicting the environmental fate and transport of curium in geological repositories.
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