Intercalation of Soil Clays with Dimethylsulfoxide

Abstract

Clays from soils of temperate and equatorial regions, containing kaolinite and complexly interstratified phyllosilicates, were intercalated with dimethylsulfoxide (DMSO) for X-ray diffraction (XRD) analysis. Washing the DMSO-clay complex with 99% methanol permitted its mounting on a glass slide instead of a porous tile for XRD. Well-resolved XRD peaks were obtained with Li-DMSO treatment. Reflections at 10, 11.2, 14.2, and 18.2A basal spacing established the presence of mica, coarse kaolinite, chlorite, and expandable 2:1 layer silicates, respectively. Several component minerals present were interstratified and did not give discrete diffraction peaks. Kaolinite with “intercalation disorder” (difficult to expand in DMSO) required a stepwise intercalation procedure that included grinding with CsCl. The grinding decreased the XRD intensity of the 11.2A peak of the kaolinite-DMSO complex. Decrease in the duration of grinding with CsCl from 15 min to two 3-min periods, washings with 8 and 4N KOAc to decrease Cs after the hydrazine treatment, and slurry-mounting the clay-DMSO intercalate on a glass slide and drying resulted in greater parallel orientation of the flakes, as shown by the more distinct and higher intensity XRD peaks than those obtained by earlier procedures. The improved intercalation procedure effectively replaced more Cs (99.5 vs. 96%) and imparted less solubility increase of the minerals (0.3-5.6% less SiO₂, 0.2-4.9% less Al₂O₃, and 0.1-0.3% less Fe₂O₃ were extracted by 0.5N NaOH and dithionite) than earlier procedures.