Structural model and de-intercalation kinetics of kaolinite-methanol-sodium stearate intercalation compound

Abstract

Kaolinite-methanol-sodium stearate intercalation compound (Ka-MeOH-SS) was prepared by intercalation of kaolinite with dimethyl sulfoxide (DMSO) followed by displacing of DMSO with methanol and methanol by sodium stearate. The sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (thermogravimetry (TGA) and differential scanning calorimetry (DSC)) and transmission electron microscopy (TEM). The results show that the basal spacing of Ka-MeOH-SS was enlarged to 45.5-47.9 Å and parts of its layers cocked and curled. Stearate ions were grafted on the methoxy groups and arrayed aslant in the interlayer space of kaolinite with an inclination angle of 47.45° to 52.17° . Sodium ions were adsorbed around the SiO4 tetrahedron and interlayer carboxylate anions, whereas some of them entered into the ditrigonal hole of tetrahedral sheets. The thermal de-intercalation of Ka-MeOH-SS includes three steps and the activation energy E is 98.3 kJ mol-1 , logarithm of pre-exponential factor lg(A / s-1 ) is 9.71 and the mechanism function is f(α) = -ln (1 - α) and G(α) = 1 - α.