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Science  06 Jun 2008:
Vol. 320, Issue 5881, pp. 1263
DOI: 10.1126/science.320.5881.1263a

Reactions between water and mineral surfaces control nearly all of Earth's surface environment—they affect weathering and thus the chemistry of the oceans and atmosphere and soil development, and are critical for understanding remediation and waste disposal. Villa et al. provide an experiment that reveals the potential complexity of these reactions, suggesting that simple models of reactions with mineral surfaces may need to be reconsidered. They used 17O nuclear magnetic resonance spectroscopy to follow the isotope exchange and dissociation reactions of a niobate cluster with seven distinct oxygen positions in aqueous solution. Analysis showed that all seven sites participate in the isotope exchange reactions in ways not easily predictable from the structure. Depending on pH, dissociation of part of the complex in some cases occurred faster than the isotope exchange reactions at most of the sites. These results suggest that the extended structure of minerals and their surface complexity need to be considered in modeling and evaluating their reactions with water. — BH

Angew. Chem. Int. Ed. 47, 10.1002/anie.200801125 (2008).

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