Intercalation Of Kaolinite Research Articles

A kaolinite-NMF-methanol intercalation compound as a versatile intermediate for further intercalation reaction of kaolinite

A kaolinite-organic intercalation compound containing methanol was proved to be a versatile host for further displacement reaction with alkylamines. Kaolinite-organic intercalation compounds with polar molecules, such as N-methylformamide (NMF) and formamide, were used as the starting materials. After stirring the kaolinite-NMF intercalation compound with methanol, the basal spacing increased to 1.11 nm. The 13C MAS NMR result of the product indicated that methanol was intercalated into kaolinite by partial displacement with NMF. By use of the methanol-treated kaolinite intercalation compound as the intermediate, alkylamines were intercalated into the interlayer space of kaolinite by displacing with methanol.

Raman microscopy of dickite, kaolinite and their intercalates†

Raman microscopy has been used to study kaolinites and dickites and their intercalates and to identify dickites in kaolins at low concentrations. During the intercalation, with potassium acetate, of a low defect structure kaolinite, several crystals provided significantly different Raman spectra. This led to the proposition that during the kaolinite intercalation process, some dickite crystals in the kaolinite were also intercalated. Raman bands at 3631 and 3640 cm–1 for the dickite were observed, corresponding well with standard dickite bands. The kaolinite intercalate showed upon intercalation, an additional Raman band at 3605 cm–1 with a consequential marked decrease in the Raman intensity of the bands at 3652, 3670, 3684, and 3693 cm–1 assigned to the vibrational modes of the inner surface hydroxyl groups. Additional Raman bands for the intercalated dickite were observed at 3609 and 3599 cm–1. These bands are attributed to the formation of a strongly hydrogen bonded complex between the inner surface hydroxyl groups of dickite and the carboxyl groups of the potassium acetate. The intensity of the 3685 cm–1 band was reduced to a minimum and the other three inner surface hydroxyls with Raman bands at 3652, 3670, and 3693 cm–1 were absent in the dickite spectra. Pronounced changes in the low frequency region for both intercalates were observed.

Experimental Transformation of Kaolinite to Halloysite

AbstractA well-characterized kaolinite has been hydrated in order to test the hypothesis that platey kaolinite will roll upon hydration. Kaolinite hydrates are prepared by repeated intercalation of kaolinite with potassium acetate and subsequent washing with water. On hydration, kaolinite plates roll along the major crystallographic directions to form tubes identical to proper tubular halloysite. Most tubes are elongated along the b crystallographic axis, while some are elongated along the a axis. Overall, the tubes exhibit a range of crystallinity. Well-ordered examples show a 2-layer structure, while poorly ordered tubes show little or no 3-dimensional order. Cross-sectional views of the formed tubes show both smoothly curved layers and planar faces. These characteristics of the experimentally formed tubes are shared by natural halloysites. Therefore, it is proposed that planar kaolinite can transform to tubular halloysite.

Intercalation of kaolinite under hydrothermal conditions

Intercalation of kaolinite with dimethylsulphoxide (DMSO) was carried out under hydrothermal conditions using a Parr bomb. The intercalated complex has been characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and thermogravimetric analysis techniques. It was found that the intercalation reaction is completed in 20 min and a high yield, ∼90%, of kaolinite/DMSO intercalate was obtained. An expansion of the original c-axis spacing of 0.714 nm in kaolinite to 1·124 nm, as a result of incorporation of DMSO molecules into the kaolinite interlayers, has been observed by XRD studies. FT-IR analyses of the intercalated complex have established the nature of interactions between the host structures and the incoming DMSO molecules. The hydrothermal method of intercalation developed in this study can also be used for other systems.

Aluminosilicate Nanocomposite Materials. Poly(ethylene glycol)−Kaolinite Intercalates

This paper reports the first example of the direct intercalation of an organic polymer into the interlamellar spaces of kaolinite. Poly(ethylene glycols) (PEG 3400 and PEG 1000) were intercalated into kaolinite by displacing dimethyl sulfoxide (DMSO) from the DMSO−kaolinite intercalate (Kao−DMSO). This was done directly from the polymer melt at temperatures between 150 and 200 °C. XRD showed that the intercalated oxyethylene units were arranged in flattened monolayer arrangements, such that the interlayer expansion was 4.0 A. Infrared analysis of Kao−PEG 3400 supported the assignment of a trans conformation to at least a portion of the (O−CH2CH2−O) groups of the PEG polymer while 13C CP and DD/MAS NMR indicated that the polymer was intercalated intact and was more constrained in the interlamellar spaces of kaolinite than it was in its bulk form. TGA/DSC analysis revealed that the complete decomposition of the organic component of the oxyethylene-based organokaolinites did not occur until greater than 1000...

Estimating the combustibility of various coals by TG-DTA

Methoxy-grafted kaolinite is an excellent organic-inorganic compound, which serves as a precursor to prepare new organic or inorganic kaolinite hybrid materials. Direct intercalation of kaolinite with dimethyl sulfoxide (DMSO), N-methylformamide (NMF) and urea (U) was achieved. All of the above intercalated kaolinites could be grafted by methoxy groups by reacting with methanol. The pre-intercalated molecules of DMSO, NMF and U blocked the grafting action at first but facilitated it at a later stage. Here, the mechanism of the structural collapse of methoxy-grafted kaolinite was proposed. Spontaneous deintercalation of small molecules such as water, ethanol, isopropanol and others was observed. Water and methanol molecules played an important role in the grafting action and also affected the structure of methoxy-grafted kaolinite. The d(001) of methoxy-grafted kaolinite was found to be in the range of 0.99–1.11 nm in wet state but constant at 0.86 nm for dry state. 13C CP/MAS NMR analysis confirmed that inner-surface hydroxyls were replaced by methoxy groups from methanol as detected by a 13C MASNMR resonance at 51 ppm assigned to methoxy groups. 13C MASNMR spectra of intercalated kaolinites confirmed that the pre-intercalated molecules were not displaced completely even though it cannot be detected by XRD. The hygroscopicity of the pre-intercalated molecules was found to affect the structure of methoxy-grafted kaolinite.

The Intercalation of Kaolinite by Alkali Halides in the Solid State: A Systematic Study of the Intercalates and their Derivatives

AbstractKaolinite: alkali halide intercalates have been successfully prepared by grinding the salt with kaolinite in the absence of water. Rate of intercalation is shown to correlate negatively with melting point of the salt. The basal dimensions of the intercalates increase with increasing size of the ion. As shown recently for kaolinite: NaCl intercalate, the layered structure survives the dehydroxylation of the kaolinite at 500°–600°C, at which point the excess alkali halide can be removed by rinsing to give an XRD-amorphous material. This amorphous material, of approximate stoichiometry MAlSiO4, reacts at surprisingly low temperatures to give crystalline phases, apparently of the same stoichiometry, with structures closely related to eucryptite (M = Li), carnegieite (M = Na), kalsilite (M = K), and leucite (M = K, Rb, Cs). The relationships between the structures of the reaction products are discussed.

Thermal decompositions of kaolinite intercalation compounds

Through a combination of X-ray diffraction and thermal analysis (simultaneous TG-DTG-DTA and quasi-isothermal TG), it was shown that the molar ratio intercalation agent/kaolinite in all intercalation compounds is approximately 1. In a saturated atmosphere of the corresponding intercalation agent, the intercalation compounds are stable up to more than 150 °C.

Infrared band frequency shifts and dipole interactions at surfaces of inorganic and organic clay intercalates

Molecules adsorbed at clay surfaces are often observed to have the frequencies of their infrared (IR) absorption bands altered by the proximity of the surfce. Using a simplified theory of dipole induction, it is shown that dispersion forces give rise to shifts or splitting of requencies which are proportional to the polarizability of the interacting dipoles and to the reciprocal of the cube of the distance between them. Additivity of bond polarizabilities makes this relationship easy to used, and it is able to account for the frequency shifts in the following four systems: hectorite and degraded phlogopite reacted with inorganic cations, dimethyl sulfoxide— and dimethyl selenoxide—kaolinite intercalates, anilinium—vermiculite intercalate, and alkylammonium—vermiculite intercalates. In the last system, the theory explains changes in the NH deformation frequencies of angled and perpendicular CN bonds that have been observed in these intercalates by showing up differences between the NH groups interacting with the clay surface. The theory can be used to determined polarizabilities if interatomic distances and IR band shifts are known. Hence it may be of potential use to comment on charges of interacting groups giving different frequencies shifts, since polarizabilities vary to some extent with charge; this is illustrated using the interaction of NH vibrations with three clays of differing charge. The theory can predict interatomic distances at surfaces from IR band shifts and polarizabilities.

Molecular Motions, Surface Interactions, and Stacking Disorder in Kaolinite Intercalates

AbstractIntercalates of Georgia well-crystallized kaolinite with formamide, N-methylformamide (NMF), and dimethylsulfoxide (DMSO) were prepared at room temperature by dispersing the clay in the organic liquid. Several physical and chemical properties of the intercalated organic molecules and the clay, while intercalated and after de-intercalation, were examined using nuclear magnetic resonance (NMR), infrared (IR), and electron paramagnetic resonance spectroscopy (EPR), and specific heat (Cp) measurements. The chemical bonding between the inner-surface hydroxyls and the organic molecules, as indicated by IR, was strongest for DMSO and weakest for formamide. The distortion of the kaolinite layer, as shown by EPR, also was greatest for DMSO and least for formamide. NMR T1 measurements indicated a relatively strong DMSO-kaolinite surface interaction that slowed down the methyl group reorientation comparable to that in bulk solid DMSO. T1 measurements indicated a weaker interaction for NMF. De-intercalation by mild heating did not return the kaolinite to its original structural state as shown by EPR and Cp. The greatest disorder was found for the DMSO de-intercalate and the least for the formamide de-intercalate. These experiments show that for sufficiently strong bonding between the clay inner surface and the intercalating molecule, the structure of the clay is capable of distortion, which is partly temporary and partly permanent. The permanent changes probably involve the introduction of stacking faults.

Interpretation of Solid state 13C and 29Si Nuclear Magnetic Resonance Spectra of Kaolinite Intercalates

Abstract13C and 29Si nuclear magnetic resonance spectroscopy with magic-angle spinning bas been used to study the short-range ordering and bonding in the structures of intercalates of kaolinite with formamide, hydrazine, dimethyl sulfoxide (DMSO), and pyridine-N-oxide (PNO). The 29Si chemical shift indicated decreasing levels of bonding interaction between the silicate layer and the intercalate in the order: kaolinite: formamide (δ) = -91.9, ppm relative to tetramethylsilane), kaolinite: hydrazine (-92.0), kaolinite: DMSO (-93.1). The 29Si signal of the kaolinite:PNO intercalate (-92.1) was unexpectedly deshielded, possibly due to the aromatic nature of PNO. The degree of three-dimensional ordering of the structures was inferred from the 29Si signal width, with the kaolinite: DMSO intercalate displaying the greatest ordering and kaolinite: hydrazine the least. 13C resonances of intercalating organic molecules were shifted downfield by as much as 3 ppm in response to increased hydrogen bonding after intercalation, and in the kaolinite: DMSO intercalate the two methyl-carbon chemical environments were non-equivalent (δ = 43.7 and 42.5).

Mechanism of Synthesis of 10-Å Hydrated Kaolinite

The synthesis of 10-A hydrated kaolinite was accomplished by: (1) direct reaction of HF with a dimethyl sulfoxide (DMSO)-kaolinite intercalate and water washing; (2) methanol washing of a DMSO-kaolinite intercalate followed by reaction with any alkali fluoride salt and water washing; and (3) room-temperature (RT) water-washing of a methanol-washed DMSO-kaolinite intercalate. In all syntheses the optimum yield required a kaolinite in which DMSO was bound strongly to the interlayer surface. In the first synthesis, water inclusion between clay layers appeared to be facilitated by the reduction of cohesive interlayer forces brought about by replacement of surface and edge OH− by F−. The fluorination reaction was accomplished either by direct reaction of HF or by HF produced through the hydrolysis of NH4F at 60°C. In the second synthesis, intercalated DMSO was replaced by methanol. F− solvated readily in methanol but not in DMSO. Consequently, F− produced through hydrolysis of the alkali fluoride salt entered the interlayer space and contributed to the fluorination reaction. Furthermore, the diffusion of methanol out of the interlayer space during the RT-washing step was slowed by F≈ solvation which aided the exchange of methanol for water. High yields of 10-A kaolinite hydrate were obtained irrespective of choice of alkali fluoride salt. The third synthesis was dependent on matching the diffusion of methanol out of the interlayer space with diffusion of water into this space. At room temperature the diffusion rates were close enough to maintain the clay in the expanded state throughout the hydration process, and high yields of 10-A kaolinite hydrate were obtained. At 60°C the diffusion rates were too dissimilar, and very low yields of hydrate were obtained.

Kaolinite Intercalation Procedure for all Sizes and Types with X-Ray Diffraction Spacing Distinctive from other Phyllosilicates

AbstractKaolinites of all kinds (fine, ‘fireclay,’ ‘type IV,’ etc.), some of which do not expand or expand incompletely with the usual intercalation methods used for comparison, are expanded completely by treatment of dry (110°C) clay with dry CsCl salt, followed by contact with hydrazine for 1 day at 65°C and then with DMSO overnight at 90°C. Comparison treatments were grinding in KOAc, soaking in hydrazine, and Li-DMSO, as well as combination of these. Following the Cs-hydrazine-DMSO treatment, the 7.2 Å spacing of 1:1 dioctahedral layer silicates shifts to 11.2 Å and the 11.2 Å/(7.2 + 11.2 Å) ratio ≃1.0. The trioctahedral 1:1 layer silicates and chlorite are not expanded by the Cs-hydrazine-DMSO procedure.

Note on the Intercalation of Kaolinite, Dickite and Halloysite by Dimethyl-Sulfoxide

AbstractVarious kaolinites, a dickite and halloysites have been treated by DMSO in presence of D2O and subsequently washed by D2O. This procedure allowed to record OD stretching bands which are due specifically to the intercalated fraction and, for the washed samples, to the fraction of the solid which has been intercalated and has subsequently collapsed.No structural difference is found between the intercalated materials prepared from the various minerals. Washing usually restores the starting mineral; however, for a non-tubular halloysite, DMSO intercalation and subsequent washing gave a product similar to kaolinite.

Mechanism for Intercalation of Kaolinite by Alkali Acetates

The relative strengths of the hydrogen bonds in kaolinite-alkali salt-water systems control kaolinite-salt interactions. A new technique for intercalation results in formation of a kaolinite-salt complex free of excess salt.

Infrared studies of hydrogen bonding interaction between kaolinite surfaces and intercalated potassium acetate, hydrazine, formamide, and urea

Expansion of kaolinite by intercalation of urea, formamide, hydrazine, and potassium acetate permits infrared studies of deuterium exchange and hydrogen bonding interaction of CO and NH 2 groups with the internal mineral surfaces. Intercalation of kaolinite with potassium acetate increases the d 001 spacing from 7.13 A. to 11.6 A., and the 3695 cm. −1 absorption band is shifted to 3600 cm. −1 owing to weak hydrogen bonding between the acetate anion and the OH groups. Intercalation of hydrazine within the kaolinite structure increases the ν(NH 2) stretching frequency from 3338 cm. −1 for the liquid to 3365 cm. −1 for the intercalated molecules. The asymmetric and symmetric ν(NH 2) stretching frequencies of liquid formamide are shifted from 3420 and 3340 cm. −1 to 3500 and 3380 cm. −1, respectively, in the formamide-kaolinite complex. In the urea-kaolinite complex, the asymmetric and symmetric ν(NH 2) stretching frequencies at 3500 and 3380 cm. −1 correspond to NH 2 groups interacting with the oxygens located on the basal tetrahedral layer; bands at 3520 and 3415 cm. −1 are assigned to similar NH 2 groups involved in weak hydrogen bonding with the inner-surface OH.