Solvent exchange in AlF{sub x} (H{sub 2}O){sup 3-x}{sub 6-x} (aq) complexes: Ligand-directed labilization of water as an analogue for ligand-induced dissolution of oxide minerals

Journal Article · Fri Aug 01 04:00:00 EDT 1997 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(97)00149-X· OSTI ID:585146

Phillips, B L; Casey, W H; Crawford, S N ^[1]

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1. Univ. of California, Davis, CA (United States)

We demonstrate, using dynamic {sup 17}O-NMR spectroscopy, that fluoride ions in the inner-coordination sphere of AlF{sub x} (H{sub 2}O){sub 6-x}{sup 3-x} (aq) complexes (0 {le} x {le} 2) progressively enhance, by orders of magnitude, the rate of exchange of waters from the innersphere to the bulk solvent. At 298K, the rate of the elementary ligand-exchange reaction increased approximately linearly with each fluoride substitution from about 2 s{sup -1} for the fully hydrated [Al(H{sub 2}O){sub 4}{sup +} (aq).] complex. A similar effect can be expected for isoelectronic complexes, such as the hydrolysis product: AlOH (H{sub 2}O){sub 5}{sup 2+} (aq). By hypothesis, a similar phenomenon accounts for fluoride-enhanced release of metals from a dissolving mineral surface. If so, it should be possible to predict the effectiveness of different adsorbed ligands to enhance dissolution of minerals from spectroscopic rate measurements on dissolved complexes, as was recently shown for aminocarboxylate ligands and NiO(s). 42 refs., 6 figs., 3 tabs.

• DOE Contract Number: FG03-96ER14629
• OSTI ID: 585146
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 15 Vol. 61; ISSN 0016-7037; ISSN GCACAK
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
58 GEOSCIENCES
GEOCHEMISTRY
LIGANDS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
REACTION KINETICS