Thickness and Surface Characteristics of Colloidal 2:1 Aluminosilicates Using an Indirect Fourier Transform of Small-Angle X-Ray Scattering Data

Abstract

Abstract--An indirect Fourier transformation applied to small-angle X-ray scattering data has been used to determine the thickness and surface properties of two common clay minerals. For an illite system, the particle density distribution function (PDDF) generated by the analysis gave a correct description of particle geometry, and the calculated electron density profile was in accordance with the theoretical electron density distribution for this mineral. This approach provides the opportunity to determine the thickness of fundamental particles of illite while avoiding the difficulties encountered in other methods. Both the PDDF and the electron density profile accurately predict the thickness of Na-montmorillonite layers, and the results suggest that an electron inhomogeneity exists at the interface of this mineral.

Invalidity of deriving interparticle distance in clay–water systems using the experimental structure factor maximum obtained by small-angle scattering

“…4. The illite used in this study has a relatively large particle thickness and low percentage (<15%) of interstratified smectite layers [10,27]; therefore, the positive charges on particle edges and the edge-face interactions should be negligible, and if they are present, the interactions are most likely present in the fine fractions. The S(q) maximum was indeed observed in the <1-µm fraction but not in the 0.1-0.15-µm fraction at the same particle concentration (10%) (Fig.…”

“…30 Laponite samples were used without further treatment. The montmorillonite and illite samples were treated according to the procedure described previously [10]. Briefly, clay samples were first treated with a pH 5 acetate buffer to remove carbonates, hydrogen peroxide (30%) to oxidize organic matter, and dithionite in citrate-bicarbonate buffer to remove free iron oxides.…”

“…Various properties have been studied to understand these minerals' colloidal behavior such as the interparticle spacing or swelling, sol/gel transition, and flocculation/aggregation behavior [1]. Small-angle scattering is a method that has been used to determine the particle dimensions, interparticle spacing, and particle organization in solution or suspension [2][3][4][5][6][7][8][9][10][11].…”