Simulation study of intercalation complexes of kaolinite with simple amides as primary intercalation reagents

Abstract

Delamination/exfoliation of book-like kaolinite particles is one of the most promising ways to produce aluminosilicate nanoscrolls. For the delamination of the kaolinite layers, multi-step intercalation/deintercalation procedures are used. In the first, direct intercalation step, the intercalation reagents are typically small organic molecules possessing high dipole moment. We modeled, evaluated and compared the incorporation features of formamide, urea and Nmethylformamide molecules into the interlayer space of kaolinite by classical molecular simulations using realistic CHARMM-based atomic force fields. Besides the determination of characteristic basal spacings of the intercalation complexes, we compared the density and orientation distributions of the guest molecules, as well as atomic pair correlation functions. From the simulations we also calculated the typical intermolecular interaction energies and estimated the translational mobility of the different substances. Our results show that urea has some preference over the other substances in multi-step, heat-treating intercalation/deintercalation procedures with kaolinite.

Montmorillonites Can Tightly Bind Glyphosate and Paraquat Reducing Toxin Exposures and Toxicity

“…Parameters and topologies within the simulations were extracted from the INTERFACE force field . The INTERFACE force field can operate as an extension of several commonly used harmonic force fields, including CHARMM, thus enabling simulations of toxin binding on organic/biomolecular and inorganic interfaces, − including montmorillonite . The topologies of glyphosate and paraquat were generated through CGENFF with low penalties using the molecular structures of the two molecules at pH 2 and 7.…”

The role of clay surfaces in the heterogeneous nucleation of calcite: Molecular dynamics simulations of cluster formation and attachment

“…Kaolinite layers can be simply regarded as uncharged reference clay layers. Nevertheless, kaolinite can be also delaminated under certain conditions (Kristóf et al, 2018). Although the spacing of the clay layers was allowed to change in the simulations, it practically did not, due to the fixed amount of the interlayer aqueous phase.…”

“…The parameters for kaolinite and montmorillonite were taken from the INTERFACE (v1.5) force field, and the other parameters including those of the interlayer Na + ions of montmorillonite were from the CHARMM database. Based on previous works (Ható et al, 2014;Kristóf et al, 2018) we found INTERFACE a suitable force field for modelling kaolinite. The CHARMM27 force field variant implemented in GROMACS (Bjelkmar et al, 2010) was used for inorganic ions.…”

Gaseous Heptanethiol Removal by a Fe3+-Phenanthroline–Kaolinite Hybrid Material

“…2:1 layer silicates such as smectites are excellent candidates for the formation of HCMs; in fact, because of their high cation exchange capacity and swelling behavior, they can intercalate even through fast one-step reaction cations or polar molecules that give peculiar properties to the resulting structure. ,,− On the other hand, the intercalation of cations and molecules in 1:1 layer silicates such as kaolinite, although it is possible, − is more difficult as the interactions are usually limited to exposed edges and sheets (adsorption), leaving the layer structure almost unchanged. In fact, unlike in smectite, kaolinite layers are bound by reactive hydrogen bonds which could not be easily broken; consequently, even if the basal spacing of kaolinite can be extended to values higher than the original 0.71 nm, it is very difficult to induce swelling through a fast one-step reaction.…”