Routine investigation of structural parameters of dioctahedral smectites by the Rietveld method

The Rietveld refinements were carried out on the X-ray powder diffraction patterns of the Cu-triethylenetetramine (Cutrien) exchanged dioctahedral smectites to avoid the problems of unknown cation species and complex hydration behavior in the interlayer. The refinements of the occupancy of octahedral iron and the LCD led to reasonable results for iron-poor purified samples. The application of the structure model to Cutrien -exchanged smectite-rich samples with natural impurities, e.g. bentonites without previous purification, showed that some important structural details of turbostratically disordered dioctahedral smectites can be determined by the Rietveld method from XRD patterns of the Cutrien -exchanged samples. The technique may be applied in routine structural characterization of raw smectites in bulk rock samples without a prior chemical analysis of purified smectite fractions.