Multinuclear complex formation between Ca(II) and gluconate ions in hyperalkaline solutions

Attila Pallagi, Éva G. Bajnóczi, Sophie E. Canton, Trudy Bolin, G. Peintler, Bence Kutus, Z. Kele, I. Pálinkó, P. Sipos

Research output: Contribution to journalArticle

18 Citations (Scopus)

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 [Ca2Gluc(OH) 3]0 (log β213 = 8.03) and [Ca 3Gluc2(OH)4]0 (log β324 = 12.39) has been proven via H2/Pt-electrode potentiometric measurements and was confirmed via XAS, 1H 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.

Original languageEnglish
Pages (from-to)6604-6611
Number of pages8
JournalEnvironmental Science and Technology
Volume48
Issue number12
DOIs
Publication statusPublished - Jun 17 2014

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Radioactive Waste
repository
radioactive waste
nuclear magnetic resonance
Actinoid Series Elements
Nuclear magnetic resonance
Ions
Atoms
actinide
ion
Freezing
Sugars
freezing
sugar
electrode
solubility
Carbon
Solubility
thermodynamics
Binding Sites

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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Multinuclear complex formation between Ca(II) and gluconate ions in hyperalkaline solutions. / Pallagi, Attila; Bajnóczi, Éva G.; Canton, Sophie E.; Bolin, Trudy; Peintler, G.; Kutus, Bence; Kele, Z.; Pálinkó, I.; Sipos, P.

In: Environmental Science and Technology, Vol. 48, No. 12, 17.06.2014, p. 6604-6611.

Research output: Contribution to journalArticle

Pallagi, Attila ; Bajnóczi, Éva G. ; Canton, Sophie E. ; Bolin, Trudy ; Peintler, G. ; Kutus, Bence ; Kele, Z. ; Pálinkó, I. ; Sipos, P. / Multinuclear complex formation between Ca(II) and gluconate ions in hyperalkaline solutions. In: Environmental Science and Technology. 2014 ; Vol. 48, No. 12. pp. 6604-6611.
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AU - Canton, Sophie E.

AU - Bolin, Trudy

AU - Peintler, G.

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