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Studies of equilibrium, structure, and dynamics in the aqueous Al(iii)-oxalate-fluoride system by potentiometry, 13C and 19F NMR spectroscopy
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2003 (English)In: Geochimica et Cosmochimica Acta, Vol. 67, no 15, 2793-2803 p.Article in journal (Refereed) Published
Abstract [en]

The AlOx1–3 (Ox = oxalate) species were identified in 0.6 M aqueous NaCl by 13C nuclear magnetic resonance (NMR). Rate constants and activation parameters for intramolecular cis/trans isomerization of the Werner-type AlOx2− complex (k(298 K) = 5 s−1, ΔH# = 67 ± 5 kJ mol−1, ΔS# = −6 ± 6 J mol−1 K−1, the rate determining step could be the breaking of the Al–O(C=O) bond) and a very slow intermolecular ligand exchange reaction of AlOx33− complex and the free ligand (k30(298 K) = 6.6 · 10−5 s−1, ΔH# = 164 ± 17 kJ mol−1, ΔS# = 225 ± 51 J mol−1 K−1, D/Id mechanism) were determined by dynamic 1D and 2D 13C NMR measurements. Mixed complexes, AlFOx, AlFOx22–, AlF2Ox−, and AlF2Ox23–, with overall stability (logβ) of 11.53 ± 0.03, 15.67 ± 0.03, 15.74 ± 0.02, and 19.10 ± 0.04 were measured by potentiometry using pH- and fluoride-selective electrodes and confirmed by 13C and19F NMR. The role of these complexes in gibbsite dissolution was modeled. The mixed Al(III)-Ox2–-F− complexes have to be considered as the chemical speciation of Al(III) in natural waters is discussed.

Place, publisher, year, edition, pages
2003. Vol. 67, no 15, 2793-2803 p.
URN: urn:nbn:se:umu:diva-9280DOI: doi:10.1016/S0016-7037(03)00099-1OAI: diva2:148951
Available from: 2008-03-18 Created: 2008-03-18 Last updated: 2011-01-13Bibliographically approved

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