Interactions of actinide analogues with naturally-occurring organic matter
- Univ. of Cincinnati, OH (United States). Dept. of Chemistry
The authors have studied the interaction of a low molecular weight alginic acid with Ca{sup 2+}, Mg{sup 2+}, Eu{sup 3+} and La{sup 3+}, using lanthanide luminescence spectroscopy (LLS) and {sup 13}C NMR. LLS results imply that nine-coordinate lanthanide ions lose six water molecules upon complexation with alginite, forming inner-sphere alginate complexes. In general, the {sup 13}C resonances in the NMR studies decreased in intensity as metal ion concentration increased, but the preference of a cation for repeating mannuronate and guluronate units (MM and GG blocks) varied greatly. The La ion binds preferentially to the GG blocks, though some binding to the MM blocks is evident, while Eu binds equally well to GG and MM blocks. Ca shows a strong preference for the GG blocks only, while Mg shows no evidence of binding to alginate at all. These preferences may be explained in terms of cation size, charge and coordination number. The diequatorial linkage pattern of sequential mannuronate residues leads to a flat ribbon-like structure with shallow cavities for the metal ions while the diaxial linkages of the guluronates allow a deeper, more size-specific cavity. Calcium has the optimum ionic radius for the GG cavities compared to the larger Eu and La ions. The smaller Mg ion does not bind at all over the concentration range studied. This could be due to its large charge density to coordination number ratio that would make dehydration of this ion and subsequent complexation by alginate thermodynamically unfavorable.
- OSTI ID:
- 377917
- Report Number(s):
- CONF-941075-; ISBN 1-55899-253-7; TRN: 96:025040
- Resource Relation:
- Conference: 18. international symposium on the scientific basis for nuclear waste management, Kyoto (Japan), 23-27 Oct 1994; Other Information: PBD: 1995; Related Information: Is Part Of Scientific basis for nuclear waste management 18. Part 1; Murakami, Takashi [ed.] [Ehime Univ., Matsuyama, Ehime (Japan). Dept. of Earth Sciences]; Ewing, R.C. [ed.] [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences]; PB: 787 p.; Materials Research Society symposium proceedings, Volume 353
- Country of Publication:
- United States
- Language:
- English
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