Influence of Synthesis Conditions on the Formation of a Kaolinitemethanol Complex and Simulation of its Vibrational Spectra

Abstract

Kaolinite is often used as a base for the synthesis of new organo-mineral nanomaterials designed for applications in industry and in environmental protection. To make the mineral structure more likely to interact with organic molecules, a kaolinite-methanol complex (KM) can be used. In the present study, different experimental procedures were tested to investigate the formation of the KM. The kaolinitedimethyl sulfoxide intercalation compound (KDS), either wet or dried, was used as a pre-intercalate. The samples obtained were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, CHNS elemental analysis, 13C CP-magic angle spinning nuclear magnetic resonance (MAS NMR), and 27Al and 29Si MAS NMR techniques. The method of density functional theory with dispersion corrections (DFT-D2) was used to explain the structure and to simulate the vibrational spectra of KM. Theoretical results were compared with experimental data. The most effective formation of the KM (d001 = 11.1 Å — wet; d001 = 8.7 Å — dried) was observed when the dried KDS precursor was used. In such conditions the degree of intercalation reached ~98% after 24 h of reaction time. As indicated by the CHNS elemental analysis, ~1/6 of the inner-surface OH groups were grafted by OCH3 groups. The esterification reaction was less efficient at higher temperatures or when wet KDS was used. In the latter case, the excess of very polar dimethyl sulfoxide molecules prevented intercalation of methanol and further grafting. Detailed analysis of the results of theoretical simulations revealed that the reaction of the KDS with methanol led to the formation of kaolinite with both grafted methoxy groups and intercalated methanol, and water molecules in the interlayer space. The spectra calculated revealed the contribution of individual vibrational modes into the complex bands, i.e. the energy of C-H vibrations was in the order: νasCHmet > νasCHmtx > νsCHmet > νsCHmtx.

Encapsulated Urea-Kaolinite Nanocomposite for Controlled Release Fertilizer Formulations

“…However, the band at 3619 cm −1 is shown to be unshifted from the original kaolinite, modified kaolinite, DMSO intercalated kaolinite, and now in the methanol intercalated kaolinite; this is in fact in agreement with 3620 cm −1 wavelength obtained by [45]. The doubly split weak broad band at 3533 cm −1 is ascribed to the externally adsorbed water as suggested by [45,50]; this band has also been considered as the OH stretching of methanol molecules and/or of water molecules formed during the esterification reaction of kaolinite inner-surface OH groups and methanol molecules [51]. The region around 3021 to 2800 cm −1 is marked by the three-split band and is ascribed to the methanol-kaolinite interaction.…”

Characterization of kaolinite-cetyltrimethylammonium chloride intercalation complex synthesized through eco-friend kaolinite-urea pre-intercalation complex

“…In the XRD pattern of ZK-UMe(wet), the complete displacement of U with Me and the formation of wet kaolinite-Me complex is clearly demonstrated by the shift of the whole (001) reflection from 1.07 nm to 1.11 nm [41]. The 1.11-nm basal spacing of the wet kaolinite-Me intercalation complex synthesized using the kaolinite-U pre-intercalation complex agrees well with the literature results with kaolinite-DMSO and kaolinite-NMF pre-intercalates [10,12,15,19,29,30,[33][34][35][36]41]. After drying the wet kaolinite-Me complexes at room temperature, the (001) reflections of the expanded phase decreased to 0.86 nm (ZK-U-Me(air-dry) sample), which is close to the value (d 001 = 0.88 nm) reported by Cheng et al [38] for similar air-dried complex prepared from kaolinite-U pre-intercalate.…”

“…From the DMSO and NMF pre-intercalates, the formation of a kaolinite-Me complex with basal spacing of 1.11-1.13 nm was established in methanol-wet state [10,12,15,19,29,30,[33][34][35][36]41], but on air-drying, a contraction down to 0.93-0.86 nm was observed [12,15,19,38,41]. Using elemental and thermal analysis results, Tunney and Detellier [7], Komori et al [15], and Matusik and Klapyta [36] calculated the values of x=0.87, x=0.36, and x=0.48, respectively, for the supposed chemical formula of In spite of the more eco-friendly behavior of U, there are only two studies reported in the literature [34,41], where the kaolinite-U pre-intercalate was used to synthesize kaoliniteMe complexes.…”

“…Using elemental and thermal analysis results, Tunney and Detellier [7], Komori et al [15], and Matusik and Klapyta [36] calculated the values of x=0.87, x=0.36, and x=0.48, respectively, for the supposed chemical formula of In spite of the more eco-friendly behavior of U, there are only two studies reported in the literature [34,41], where the kaolinite-U pre-intercalate was used to synthesize kaoliniteMe complexes. In our previous work with U [41], we obtained the same methanol-wet state (with the basal spacing of 1.12 nm) as prepared earlier in the literature using the kaolinite-DMSO and kaolinite-NMF pre-intercalates [10,12,15,19,29,30,[33][34][35][36]. However, the drying of our methanol-wet complex leaded to a somewhat different methoxylated kaolinite structure with x=0.3, which was far below the theoretical upper limit ratio of methoxy functionalization (x=1) of the inner surfaces.…”

Effect of Intercalation Agents on Morphology of Exfoliated Kaolinite

“…Simultaneously, the variety of the guest species that are intercalated into kaolinite layers has also been extended. As an intermediate to further intercalate large guest species, methoxy-modified kaolinite has been paid great attention to [15,[22][23][24][25]. So far, the intercalation of kaolinite by inserting series alkylamines [15,22,26], series quaternary ammonium salts [23,27], series silanes with an amino group, benzyl alkyl ammonium chlorides [28,29], series fatty acids and salts [30,31] into kaolinite layers by taking a methanol-grafted kaolinite compound as a precursor has been successfully performed.…”