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Comparison of Techniques for Determining the Fractal Dimensions of Clay Minerals

Published online by Cambridge University Press:  28 February 2024

Kalumbu Malekani ,
James A. Rice  and
Jar-Shyong Lin
Kalumbu Malekani
Affiliation:
Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007
James A. Rice
Affiliation:
Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007
Jar-Shyong Lin
Affiliation:
Center for Small-Angle Scattering, Solid-State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
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Abstract

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Small-angle X-ray scattering (SAXS), adsorption and nuclear magnetic resonance (NMR) techniques were used to determine the fractal dimensions (D) of 3 natural reference clays: 1) a kaolinite (KGa-2); 2) a hectorite (SHCa-1), and 3) a Ca-montmorillonite (STx-1). The surfaces of these clays were found to be fractal with D values close to 2.0. This is consistent with the common description of clay mineral surfaces as smooth and planar. Some surface irregularities were observed for hectorite and Ca-montmorillonite as a result of impurities in the materials. The SAXS method generated comparable D values for KGa-2 and STx-1. These results are supported by scanning electron microscopy (SEM). The SAXS and adsorption methods were found to probe the surface irregularities of the clays while the nuclear magnetic resonance (NMR) technique seems to reflect the mass distribution of certain sites in the material. Since the surface nature of clays is responsible for their reactivity in natural systems, SAXS and adsorption techniques would be the methods of choice for their fractal characterization. Due to its wider applicable characterization size-range, the SAXS method appears to be better suited for the determination of the fractal dimensions of clay minerals.

Keywords

AdsorptionClayFractalNMRSmall-angle x-ray scattering
Type
Research Article
Information
Clays and Clay Minerals , Volume 44 , Issue 5 , October 1996 , pp. 677 - 685
Copyright
Copyright © 1996, The Clay Minerals Society

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