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Multinuclear Complex Formation between Ca(II) and Gluconate Ions in Hyperalkaline Solutions

Pallagi, Attila; Bajnoczi, Eva G.; Canton, Sophie LU ; Bolin, Trudy; Peintler, Gabor; Kutus, Bence; Kele, Zoltan; Palinko, Istvan and Sipos, Pal (2014) In Environmental Science & Technology 48(12). p.6604-6611
Abstract
Alkaline solutions containing polyhydroxy carboxylates and Ca(II) are typical in cementitious radioactive waste repositories. Gluconate (Gluc(-)) is a structural and functional representative of these sugar carboxylates. In the current study, the structure and equilibria of complexes forming in such strongly alkaline solutions containing Ca2+ and gluconate have been studied. It was found that Gluc(-) significantly increases the solubility of portlandite (Ca(OH)(2)(s)) under these conditions and Ca2+ complexes of unexpectedly high stability are formed. The mononuclear (CaGluc(+) and [CaGlucOH](0)) complexes were found to be minor species, and predominant multinuclear complexes were identified. The formation of the neutral... (More)
Alkaline solutions containing polyhydroxy carboxylates and Ca(II) are typical in cementitious radioactive waste repositories. Gluconate (Gluc(-)) is a structural and functional representative of these sugar carboxylates. In the current study, the structure and equilibria of complexes forming in such strongly alkaline solutions containing Ca2+ and gluconate have been studied. It was found that Gluc(-) significantly increases the solubility of portlandite (Ca(OH)(2)(s)) under these conditions and Ca2+ complexes of unexpectedly high stability are formed. The mononuclear (CaGluc(+) and [CaGlucOH](0)) complexes were found to be minor species, and predominant multinuclear complexes were identified. The formation of the neutral [Ca(2)Gluc(OH)(3)](0) (log beta(213) = 8.03) and [Ca(3)Gluc(2)(OH)(4)](0) (log beta(324) = 12.39) has been proven via H-2/Pt-electrode potentiometric measurements and was confirmed via XAS, H-1 NMR, ESI-MS, conductometry, and freezing-point depression experiments. The binding sites of Gluc- were identified from multinuclear NMR measurements. Besides the carboxylate group, the O atoms on the second and third carbon atoms were proved to be the most probable sites for Ca2+ binding. The suggested structure of the trinuclear complex was deduced from ab initio calculations. These observations are of relevance in the thermodynamic modeling of radioactive waste repositories, where the predominance of the binuclear Ca2+ complex, which is a precursor of various high-stability ternary complexes with actinides, is demonstrated. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Environmental Science & Technology
volume
48
issue
12
pages
6604 - 6611
publisher
The American Chemical Society
external identifiers
  • wos:000337646000011
  • scopus:84902590911
ISSN
1520-5851
DOI
10.1021/es501067w
language
English
LU publication?
yes
id
8fb2dd66-0a10-4978-ab02-05a2a2d7f9bd (old id 4609545)
date added to LUP
2014-08-26 11:04:52
date last changed
2017-10-29 03:56:22
@article{8fb2dd66-0a10-4978-ab02-05a2a2d7f9bd,
  abstract     = {Alkaline solutions containing polyhydroxy carboxylates and Ca(II) are typical in cementitious radioactive waste repositories. Gluconate (Gluc(-)) is a structural and functional representative of these sugar carboxylates. In the current study, the structure and equilibria of complexes forming in such strongly alkaline solutions containing Ca2+ and gluconate have been studied. It was found that Gluc(-) significantly increases the solubility of portlandite (Ca(OH)(2)(s)) under these conditions and Ca2+ complexes of unexpectedly high stability are formed. The mononuclear (CaGluc(+) and [CaGlucOH](0)) complexes were found to be minor species, and predominant multinuclear complexes were identified. The formation of the neutral [Ca(2)Gluc(OH)(3)](0) (log beta(213) = 8.03) and [Ca(3)Gluc(2)(OH)(4)](0) (log beta(324) = 12.39) has been proven via H-2/Pt-electrode potentiometric measurements and was confirmed via XAS, H-1 NMR, ESI-MS, conductometry, and freezing-point depression experiments. The binding sites of Gluc- were identified from multinuclear NMR measurements. Besides the carboxylate group, the O atoms on the second and third carbon atoms were proved to be the most probable sites for Ca2+ binding. The suggested structure of the trinuclear complex was deduced from ab initio calculations. These observations are of relevance in the thermodynamic modeling of radioactive waste repositories, where the predominance of the binuclear Ca2+ complex, which is a precursor of various high-stability ternary complexes with actinides, is demonstrated.},
  author       = {Pallagi, Attila and Bajnoczi, Eva G. and Canton, Sophie and Bolin, Trudy and Peintler, Gabor and Kutus, Bence and Kele, Zoltan and Palinko, Istvan and Sipos, Pal},
  issn         = {1520-5851},
  language     = {eng},
  number       = {12},
  pages        = {6604--6611},
  publisher    = {The American Chemical Society},
  series       = {Environmental Science & Technology},
  title        = {Multinuclear Complex Formation between Ca(II) and Gluconate Ions in Hyperalkaline Solutions},
  url          = {http://dx.doi.org/10.1021/es501067w},
  volume       = {48},
  year         = {2014},
}