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 SiO 4 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.

Thermodynamic Mechanism and Interfacial Structure of Kaolinite Intercalation and Surface Modification by Alkane Surfactants with Neutral and Ionic Head Groups

“…The magnitude of calculated intercalation free energies for the three surfactants agrees with the experimentally observed intercalation trend that the CTAC can more easily achieve the intercalation and surface modification of methanol preintercalated kaolinite compared with stearate and dodecylamine. 10,12,38 It is interesting to note that the PMF of CTAC (Figure 2) has the bumpy feature before completely entering the kaolinite interlayer. The local maximums of the free energies along the reaction coordinate represent the energy barrier when CTAC continually move into the interlayer, which are related with the transfer of the head group N(CH 3 ) 3 + of CTAC above the adjacent ditrigonal cavities on the siloxane surface in the kaolinite interlayer.…”

Biomimetic Tremelliform Ultrathin MnO2/CuO Nanosheets on Kaolinite Driving Superior Catalytic Oxidation: An Example of CO

“…The specific benefits of kaolinite come from its distinct structure, natural abundance, and relatively low cost. Structurally, kaolinite has a basic unit cell consisting of a tetrahedral silica sheet and an octahedral alumina sheet along the c -axis . Kaolinite exhibits relatively high reactivity toward chemical modification due to the presence of surface hydroxyl groups.…”

Liquid-Phase Exfoliation of Kaolinite by High-Shear Mixer with Graphite Oxide as an Amphiphilic Dispersant

“…However, only a limited number of micromolecules can be directly intercalated, such as dimethyl sulfoxide, urea, and N -methylformamide, owing to the adjacent layers being linked by hydrogen bonds, in which the interlayer spacing is difficult to be enlarged. With pre-intercalation of micromolecules, more larger molecules have been successfully intercalated, such as methanol, − series alkylamines, series quaternary ammonium salts, , and series fatty acids and salts . However, the chemical intercalation process is usually harsh and has lower intercalation rate, consumes more time and energy, and is environmentally unfriendly.…”

“…With preintercalation of micromolecules, more larger molecules have been successfully intercalated, such as methanol, 23−25 series alkylamines, 26 series quaternary ammonium salts, 27,28 and series fatty acids and salts. 29 process is usually harsh and has lower intercalation rate, consumes more time and energy, and is environmentally unfriendly.…”