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Geochimica et Cosmochimica Acta, 2000
Rate coefficients for steady exchange of oxygens between sites in the AlO4Al12 (OH) 24 (H2O) 127+... more Rate coefficients for steady exchange of oxygens between sites in the AlO4Al12 (OH) 24 (H2O) 127+(aq)(Al13) complex and bulk solution were determined over the temperature range of 9–19° C and 4.6< pH< 5.4 using 17O-NMR. The molecule has 12 equivalent ...
![Research paper thumbnail of Mechanisms for fluoride-promoted dissolution of bayerite [β-Al(OH)3(s)] and boehmite [γ-AlOOH]: 19F-NMR spectroscopy and aqueous surface chemistry](https://attachments.academia-assets.com/54128410/thumbnails/1.jpg)
](Geochimica et Cosmochimica Acta, 1999
Some reactions that control the dissolution of bayerite [-Al(OH) 3 (s)] and boehmite [␥-AlOOH] w... more Some reactions that control the dissolution of bayerite [-Al(OH) 3 (s)] and boehmite [␥-AlOOH] were identified by comparing the adsorption chemistry, the dissolution rates, and solid-state 19 F-NMR spectra of the reacting surfaces. The 19 F-NMR spectra of bayerite distinguish two sites for fluoride reaction that vary in relative concentration with the total adsorbate density. One resonance at Ϫ131 ppm is assigned to fluoride bridges and the other resonance at Ϫ142 ppm is assigned to fluoride at terminal sites. These same resonances are observed on boehmite, in addition to a third resonance at Ϫ151 ppm that is tentatively assigned to aqueous AlF n (H 2 O) 6Ϫn (3Ϫn)ϩ (aq) complexes in pores. Peak broadening due to dipolar coupling between surface fluorides at high loading indicates that these sites are in close proximity.
Geochimica et Cosmochimica Acta, 1999
Rate parameters are reported for exchange of hydration waters from the inner coordination sphere ... more Rate parameters are reported for exchange of hydration waters from the inner coordination sphere of Al(III)-sulfosalicylate [Al(sSal) ϩ ] and Al(III)-salicylate [Al(Sal) ϩ ] complexes to bulk solution as determined with 17 O-NMR. The rate parameters for the Al(sSal) ϩ complex are:
Geochimica et Cosmochimica Acta, 1998
Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere ... more Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere of Al(III)-methylmalonate complexes with bulk solution as determined via 17 O-NMR. Surprisingly, water molecules in the thermodynamically less-stable complexes containing six-membered chelates are much more labile than those in five-membered oxalate-Al(III) complexes. The rate parameters for the Al(mMal) ϩ complex are:
We are observing an sharp evolution within low-temperature geochemistry away from thermodynamics ... more We are observing an sharp evolution within low-temperature geochemistry away from thermodynamics and deep geologic time toward molecular processes, particularly those at mineral or bacterial surfaces, and disequilibria. This evolution has led to a new cooperation between Earth scientists and inorganic chemists who synthesize aqueous metal-(hydr)oxide clusters as models for enzyme centers and hydrolytic products. If geochemists too can embrace these methods, we can create experimental models to answer some of the key questions posed about minerals and their reactions with aqueous solutions. In this paper we lay out the areas where there is overlap in these two fields using particular examples and emphasize how skills from each subdiscipline can benefit the whole.
Geochimica et Cosmochimica Acta, 2000
Rate coefficients for steady exchange of oxygens between sites in the AlO4Al12 (OH) 24 (H2O) 127+... more Rate coefficients for steady exchange of oxygens between sites in the AlO4Al12 (OH) 24 (H2O) 127+(aq)(Al13) complex and bulk solution were determined over the temperature range of 9–19° C and 4.6< pH< 5.4 using 17O-NMR. The molecule has 12 equivalent ...
Geochimica et Cosmochimica Acta, 1999
Some reactions that control the dissolution of bayerite [-Al(OH) 3 (s)] and boehmite [␥-AlOOH] w... more Some reactions that control the dissolution of bayerite [-Al(OH) 3 (s)] and boehmite [␥-AlOOH] were identified by comparing the adsorption chemistry, the dissolution rates, and solid-state 19 F-NMR spectra of the reacting surfaces. The 19 F-NMR spectra of bayerite distinguish two sites for fluoride reaction that vary in relative concentration with the total adsorbate density. One resonance at Ϫ131 ppm is assigned to fluoride bridges and the other resonance at Ϫ142 ppm is assigned to fluoride at terminal sites. These same resonances are observed on boehmite, in addition to a third resonance at Ϫ151 ppm that is tentatively assigned to aqueous AlF n (H 2 O) 6Ϫn (3Ϫn)ϩ (aq) complexes in pores. Peak broadening due to dipolar coupling between surface fluorides at high loading indicates that these sites are in close proximity.
Geochimica et Cosmochimica Acta, 1999
Rate parameters are reported for exchange of hydration waters from the inner coordination sphere ... more Rate parameters are reported for exchange of hydration waters from the inner coordination sphere of Al(III)-sulfosalicylate [Al(sSal) ϩ ] and Al(III)-salicylate [Al(Sal) ϩ ] complexes to bulk solution as determined with 17 O-NMR. The rate parameters for the Al(sSal) ϩ complex are:
Geochimica et Cosmochimica Acta, 1998
Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere ... more Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere of Al(III)-methylmalonate complexes with bulk solution as determined via 17 O-NMR. Surprisingly, water molecules in the thermodynamically less-stable complexes containing six-membered chelates are much more labile than those in five-membered oxalate-Al(III) complexes. The rate parameters for the Al(mMal) ϩ complex are:
We are observing an sharp evolution within low-temperature geochemistry away from thermodynamics ... more We are observing an sharp evolution within low-temperature geochemistry away from thermodynamics and deep geologic time toward molecular processes, particularly those at mineral or bacterial surfaces, and disequilibria. This evolution has led to a new cooperation between Earth scientists and inorganic chemists who synthesize aqueous metal-(hydr)oxide clusters as models for enzyme centers and hydrolytic products. If geochemists too can embrace these methods, we can create experimental models to answer some of the key questions posed about minerals and their reactions with aqueous solutions. In this paper we lay out the areas where there is overlap in these two fields using particular examples and emphasize how skills from each subdiscipline can benefit the whole.