engleski

Application of NMR techniques in characterization of model clays, sediments and soils

Present work is a continuation of long term studies of conditions necessary for initial clay formation in model systems, containing organic acids, amino acids, carbohydrates, aluminum ion and silicic acid. Different NMR techniques are used as complementary to other analytical methods. The advantage in use of solid state NMR spectroscopy is that it is not necessary to dissolve compounds, sediments and soils. Solution NMR techniques can be used as well, but are suitable for easily soluble compounds. Our preliminary work was performed using solid 27Al MAS NMR, 29Si MAS NMR and 23Na MAS NMR. Some examples of NMR spectra of model compounds: Al hydroxo phthalates and Al silicates will be presented to show different coordination. Aluminum hydroxo phthalates exhibit broad multi component 27Al MAS NMR spectra centered at 0 ppm, characteristic of non-framework hexa-coordinated octahedral Al atoms. Spectra of alumino silicates consist of two narrow resonances, appearing at 0 and 54 ppm, characteristic of non framework (octahedral) and framework (tetrahedral) Al atoms. 29Si MAS NMR spectra were broad, of varying overall intensity, covering the range between -75 to 100 ppm. Si atoms are located predominantly in the tetrahedral framework. It is our aim for the future work to apply our experience obtained on model systems to natural sediments and soils, particularly from large Kupa River drainage basin, which extends from Slovenia, Croatia to West Bosnia and has strong influence on Sava River. In the field of water policy, according to Decision No. 2455/2001/EC of the European Parliament and of the Council, numerous organic and inorganic substances have to be measured, both in water and in sediments. Therefore we hope to initiate application of 13C-, 15N-, 1H-, 31P-, 27Al-, 29Si- and 23Na- NMR techniques on characterization of natural sediments, in collaboration with Hungary.

27Al MAS NMR; 29Si MAS NMR; model clay formation; sediments

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