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Article Dans Une Revue Chemical Geology Année : 2019

Formation of mixed Eu(III)-CO3 -fulvic acid complex: Spectroscopic evidence and NICA-Donnan modeling

Résumé

Humic substances impact the fate of radionuclides in the environment. The formation of mixed complexes between lanthanides(III), carbonates, and humic substances is still a matter of debate and further studies are needed. Time-resolved luminescence spectroscopy (TRLS) is used to evidence the presence of Eu(III)-CO 3-SRFA ternary complexes in media representative of environmental conditions. The evolutions of the Eu(III) lumi-nescence spectra from the 5 D 0 → 7 F 0 to the 5 D 0 → 7 F 2 transitions are showing modifications of the asymmetry ratio-area ratio of the 5 D 0 → 7 F 2 over the 5 D 0 → 7 F 1 transition-that indicates the presence of several species in addition to the EuCO 3 + and Eu-SRFA complexes. The occurrence of bi-exponential decay times, with one decay time faster than the one from Eu 3+ , is typical of the occurrence of fulvic complex, even in the presence of carbonate. The analyses of the indirect excitation of the Eu-CO 3-SRFA system are used to build complexation isotherms varying either SRFA or total carbonate concentrations in the framework of the NICA-Donnan modeling of the Eu(III)-SRFA system. In view of the restricted pH range, no strict attribution to the different possible types of sites can be done. Different complex(es) formations are considered and discussed.

Domaines

Géochimie
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Dates et versions

hal-02406003 , version 1 (31-03-2021)

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Yasmine Z. Kouhail, Marc F Benedetti, Pascal E Reiller. Formation of mixed Eu(III)-CO3 -fulvic acid complex: Spectroscopic evidence and NICA-Donnan modeling. Chemical Geology, 2019, 522, pp.175-185. ⟨10.1016/j.chemgeo.2019.05.032⟩. ⟨hal-02406003⟩
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