Role of Impurities in Kaolinite Intercalation and Subsequent Formation of Nanoscrolls

Abstract

Kaolinite (Kaol)−methanol (MeOH) compounds (Kaol-Me) are widely used as the starting materials for further intercalation. The conventional approach to prepare Kaol-Me compounds is to wash dimethyl sulfoxide (DMSO)-intercalated Kaol (Kaol-DMSO) for 16 days, and MeOH must be refreshed every day. Herein, we report a new and much more efficient method to prepare Kaol-Me from Kaol-DMSO by the promotion of AlCl 3 under mild conditions, and the corresponding mechanism is investigated. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and X-ray fluorescence characterization results reveal that the electric double layer resulting from the impurities absorbed on the kaolinite surface prevents weakly polar molecules from entering the kaolinite interlayers, which is probably the key reason that MeOH must be refreshed daily in the preparation of Kaol-Me compounds. After being treated with HCl to remove the impurities, Kaol-Me-HCl was successfully intercalated by cetyltrimethyl ammonium bromide and subsequently predominantly curled into nanoscrolls.

Integrating Structural and Thermodynamic Mechanisms for Methanol Intercalated Kaolinite Nanoclay: Experiments and Density Functional Theory Simulation

“…If the activity of free DMSO can be reduced, the grafting process will be accelerated. For example, AlCl 3 and DMSO could form complexes to decrease the combination of DMSO and kaolinite; , this result probably can explain the experiment that highly efficient kaolinite nanoscrolls could be prepared by catalysis of AlCl 3 . , …”

“…On the contrary, the final structures of intercalated Kaol were 0.852–0.870 nm with more water molecules when DHK was used as the precursor. Additionally, the methanol molecules (MeOH) grafted onto octahedral sheets of kaolinite in the form of a methoxy group (MeO) as eq . ,− ,− Al ( Kaol ) − OH + MeOH → Al ( Kaol ) − normalO − Me + H 2 normalO …”

“…(IV) The application of methanol intercalated Kaol. To date, researches mainly carried out studies on aspects I–III, − while the structure analysis and structure variation of the intercalation process is unclear. The most common method to prepare methanol intercalated Kaol is using DMSO/urea/potassium acetate intercalated Kaol mixed with daily replaced fresh methanol for at least 7 days at room temperature .…”

“…Recently, Zhang found a similar accelerating effect of the acid on the formation of methanol intercalated kaolinite. The acid could destroy the impurities absorbed on the kaolinite surface which prevents weakly polar molecules from entering the kaolinite interlayers through the electric double layer …”