Comparison of complexed species of Eu in alumina-bound and free polyacrylic acid: A spectroscopic study

The speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAA ads) was studied at pH 5 in 0.1 M NaClO 4. Structural parameters were obtained from 7F 0 → 5D 0 excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu L III-edge extended X-ray ab...

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Bibliographic Details
Published in:Journal of colloid and interface science 2006-08, Vol.300 (2), p.482-490
Main Authors: Montavon, G., Hennig, C., Janvier, P., Grambow, B.
Format: Article
Language:English
Subjects:
Adsorption
Chemical Sciences
Chemistry
Exact sciences and technology
EXAFS
FTIR
General and physical chemistry
LIFS
Polyacrylic acid
Radiochemistry
Speciation
Surface physical chemistry
Ternary system
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Summary:The speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAA ads) was studied at pH 5 in 0.1 M NaClO 4. Structural parameters were obtained from 7F 0 → 5D 0 excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu L III-edge extended X-ray absorption fine structure (EXAFS) spectra. The coordination mode was also investigated by infrared spectroscopy. To elucidate the nature of the complexed species, Eu–acetate complexes were used as references. The spectroscopic techniques show that two carboxylate groups with 2–3 (EuPAA) and 4–5 (EuPAA ads) water molecules are coordinated to Eu in the first coordination sphere. For EuPAA ads, the coordination between carboxylate groups and Eu appears to be bidendate. A similar coordination is probable for EuPAA but the EXAFS data indicate a slightly distorted coordination. The results show that the degree of freedom of carboxylate groups is not the same for free or adsorbed PAA. For PAA, the degree of freedom is constrained by the flexibility of the methylene chain. When PAA is adsorbed on alumina, the polymer chains cannot any more be treated as independent chains. One may rather assume formation of aggregates that form an organic layer at the mineral surface presenting a complex arrangement of carboxylate groups. The question addressed in this study is to assess the effect of the adsorption of an organic polyelectrolyte onto a mineral phase on its complexation properties for metal ions.
ISSN:0021-9797
1095-7103
DOI:10.1016/j.jcis.2006.04.053