Uptake of dissolved material by mineral surfaces is an important process controlling the mobility of nutrients and contaminants in natural, disturbed, and agricultural systems. The effectiveness of sorbents depends critically on the uptake mechanism, which is often difficult to ascertain due to the chemical complexity and heterogeneous nature of interfaces. NMR spectroscopy can provide information on the bonding of sorbates, especially for the many light elements which have NMR-active isotopes. Advances particularly in the application of double resonance methods have improved the utility of NMR for probing the spatial environment of sorbates. These techniques provide information on dipolar coupling between nuclei, which helps assign peaks and identify coordination environments. Examples include 1H/31P heteronuclear correlation to identify apatite precipitates from Ca/phosphate co-sorption, and 31P/?27Al double resonance for surface coordination of phosphate to Al-oxyhydroxides. In addition, advances in understanding paramagnetic effects may enable NMR in systems previously considered ill-suited, as demonstrated by recent work on P sorbed by Fe-oxyhydroxides. Challenges remain, including the insensitivity of NMR and the resulting large amounts of time required to investigate interfacial systems.

Advances in application of NMR methods to reactions at mineral/fluid interfaces

245th National Meeting (2013)

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