Kaolinites 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.

When aqueous dispersions of Na+-smectite or n-butylammonium-vermiculite react with sulfate salts of Fe(II), Co(II), or Ni(II) bipyridyl or 1, 10-phenanthroline complexes in excess of the cation-exchange capacities, intersalated phases with spacings of about 29.5 Å are obtained. Thermal decomposition of the intersalated complex cations affords expanded phases with a d(001) spacing near 18 Å for the smectites and near 28 Å for the vermiculites. These phases are stable to temperatures of at least 550°C. Nitrogen surface areas of the fired products are as high as 400 m2/g.

Silica-intercalated hectorite with an 001 spacing of 12.6 Å and a N2 BET surface area of 220 m2/ g was prepared by hydrolysis and oxidation at 500°C of hectorite containing a silicon acetylacetonate complex. The intercalate swelled to higher spacings upon adsorption of water, glycerol, and pyridine, but the silica was not expelled when the interlayers swelled and contracted in successive adsorption/desorption cycles. The surface area measured by isobutane adsorption agrees with the N2BET surface area, suggesting that the interlayers are available for adsorption of aliphatic hydrocarbons. The intercalated silica did not inhibit the ability of the interlayers to enter into cation-exchange reactions, as judged from Cu2+-binding experiments. Infrared studies of NH3-, pyridine-, and NO2-adsorption indicate the presence of Bronsted acidity and the absence of Lewis acidity in the interlayer regions.

The thermal decomposition of a kaolinite:dimethyl sulfoxide intercalate has been studied by thermogravimetry. The decomposition is complete by 175°C and has a ΔH of 58 ± 5 kJ/mole of dimethyl sulfoxide. For the first 70–80% of the reaction a plot of log(l — α) vs. time is linear, where α is the reaction fraction complete. A two-dimensional, contracting-circle type of mechanism is consistent with this linearity, provided that the nucleation process is considered to be exponential rather than instantaneous. An activation energy of 105 ± 8 kJ/mole of dimethyl sulfoxide has been derived. This value is inconsistent with the simple assumption that the rate-determining step is the freeing of single organic molecules from their bonding to the clay layers. The mechanism of this decomposition is different from that found for kaolinite: N-methyl formamide, and the activation energy is considerably greater than that found for that material (30 ± 3 kJ/mole).

Montmorillonite-aminocaproic acid complexes (monomer complexes) were prepared by the intercalation of 6-aminocaproic acid to various homoionic (Na+, Ca2+, Mg2+, Co2+, and Cu2+) montmorillonites. Infrared spectra of the monomer complexes indicated that the interaction between the exchangeable cations and the 6-aminocaproic acid increased in the following order: Na-, Ca-, and Mg- < Co- < Cu-montmorillonite-aminocaproic acid complex. Montmorillonite-nylon complexes (polymer complexes) were prepared by thermal treatment of the monomer complexes, which was confirmed by X-ray powder diffraction and infrared spectroscopy the results of which indicated the condensation of 6-aminocaproic acid in the interlayer space.

Thermal degradation of montmorillonite-nylon complexes was studied by thermogravimetry. It was found that the thermal stability of the polymer complexes increased in the following order: Cu- < Co- < Na- < Mg- < Ca-montmorillonite-nylon complex.

It was suggested that the difference in thermal stability depended upon the length of the polymer chain which might be influenced by the interaction between the exchangeable cations and the 6-aminocaproic acid. The activation energy for the thermal degradation of each montmorillonite-nylon complex was obtained, and the value for Cu-montmorillonite-nylon complex was smaller than that for the other cation-exchanged montmorillonite-nylon complexes.

Several new salt intercalation complexes of halloysite have been prepared and characterized using X-ray powder diffraction techniques taking into account both the position and the shape of the d001 peaks. The amount of intercalated ion in some fully complexed halloysites has been directly determined using conventional analytical techniques. The results show that less than half of the theoretical amount of salt is intercalated into the clay; the amount of salt depending on its nature and, where hydrolyzable ions are present, on the pH. Infrared spectra taken of some complexes give an indication of the nature of the interaction within interlayer space and elsewhere. The interactions are weak and are either dipolar attractions or hydrogen bonds. The ions which show the greatest tendency to intercalate with halloysite are water structure-breaking cations or hydrogen-bonding anions.

Intercalation compounds of styrene and quaternary ammonium montmorillonite were prepared by immersion of the clay in styrene monomer. The intercalation of stearyltrimethylammonium (CH3(CH2)17N(CH3)3+)-montmorillonite and styrene showed an expansion of the basal spacing to a constant value of ∼32 Å after immersion for 10 days. After polymerization, the amount of polystyrene in the interlayer region was determined by thermal gravimetric analysis. Styrene adsorption initially increased with increasing quaternary ammonium cation and then became approximately constant when loading of the quaternary ammonium cation exceeded 100 meq/100 g clay. The volume resistivity of the stearyltrimethylammonium-montmorilionite-polystyrene complex, which was determined with a high resistance meter, was greater than that of both the quaternary ammonium-montmorillonite and the montmorillonite, and increased in proportion to the amount of polymer adsorbed. These data indicate that polystyrene improved the insulating properties of the clay films.

Silica has been intercalated in swelling clays by hydrolysis and/or oxidation of tris(acetylacetonato)siIicon(IV) cations, Si(acac)3+, and polychlorosiloxanes, (-SiOCl2-)n, in the interla-mellar regions of the minerals. The Si(acac)3+ ions have been placed on the interlamellar surfaces by ion exchange and by in situ reaction of the acetylacetone-solvated clays with SiCl4. The (-SiOCl2-)n polymers were formed in the interlayers by reaction of adsorbed benzaldehyde with SiCl4. The optimum (001) spacing observed after firing the clays in air at 500°C (12.6 Å) corresponds to the presence of a monolayer of siloxane chains. Nitrogen BET surface areas range from 40 to 240 m2/g, depending on the amount of internal surface covered by the intercalated silica. In some cases, highly ordered products were formed which exhibit four orders of (00ℓ) reflection. Interstratified products with d(001) values between 9.6 and 12.6 Å exhibit surface areas consistent with the presence of a random mixture of totally collapsed interlayers and interlayers containing siloxane monolayers. Attempts to achieve silica intercalation by hydrolysis of SiCl4 in the clay interlayers were not productive.

Polycations of limited molecular size were prepared from 0.1 M solutions of Fe(III)(NO3)3 and A1(NO3)3 by ultrafiltration. Various amounts of the polycations were added to Na-kaolinite, Na-mont-morillonite, and a Na-soil clay and the effect on the flocculation of the clay and electrophoretic mobility compared. Flocculation occurred just before zero net charge was obtained. Addition of further polycation resulted in the dispersion of clay with a net positive charge. The Al polycations possessed a high positive charge (0.49 per gram atom of Al), and their interaction with the clays indicated a planar shape. Adsorption of Al polycations decreased markedly the cation-exchange capacities of the kaolinite and the soil clay but had little effect on surface areas determined by low-temperature N2 adsorption. The Fe polycations were spheres 10–100 Å in diameter with a positive charge of 0.2 per gram atom. The surface areas of the kaolinite and the soil clay were substantially increased by the addition of the Fe polycations but their cation-exchange capacities were reduced by one fifth. Al polycations increased the surface areas of the montmorillonite (to 300 m2) presumably by propping open the interlamellar spaces and rendering the a-b planes accessible for nitrogen adsorption. The Al polycations in interlamellar spaces prevented collapse to 14 Å on heating to 150°C. There was no evidence of regular interlayer Fe as might be anticipated from the size of the spheres.

The coarse (2-0.2 μm) and fine (<0.2 μm) size fractions of several soil and reference kaolinite samples were completely intercalated and expanded to 11.2 Å using a simplified CsCl-hydrazine-di-methylsulfoxide (DMSO) treatment. Rapid equilibration of the clay in hot (80°C) hydrazine monohydrate and hot (100°C) DMSO, and the use of ceramic tile mounts, limited the sample pretreatment time to only 15 min. The fine size fraction of kaolinite may be X-rayed immediately after pretreatment, though analysis of the sample 2 or 12 hr after pretreatment produced more intense, sharp basal reflections. This difference may be due to a better ordering of the DMSO-kaolinite complex with time and to a drying of the excess DMSO. The coarse size fraction of kaolinite did not entirely expand to 11.2 Å when analyzed immediately after pretreatment. A 9.6-Å peak was also present and possibly represents a mixed layering of expanded and nonexpanded kaolinite layers. The larger crystals seem to require additional time for the reaction to become complete as evidenced by the presence of an intense, sharp 11.2-Å peak and absence of the 9.6-Å peak when the coarse clay was analyzed 2 or 12 hr after sample pretreatment. Kaolinite particles <50 μm did not react completely even when they were analyzed 24 hr after pretreatment. Therefore, this technique should be limited to <2-μm particles.

Three montmorillonite samples, from Wyoming (particle size <0.2 µm, 4.6 wt. % Fe2O3), Greece (<14 µm, 6.5 wt. % Fe2O3), and Poland (0.5 wt. % Fe2O3, two fractions <2 µm and 2–10 µm) were intercalated with hydroxy-Al species. The amount of hydroxy-Al cations exchanged by the clays depended on the particle size: it decreased from 31 wt. % Al2O3 for 0.2 µm in size to 22.6 wt. % for >2 µm. The X-ray powder diffraction (XRD) pattern showed that most of the material was not intercalated after refluxing at 80°C for 2 hr; several redispersions of the pillared clay in hot water were required to obtain a single sharp XRD line at 18.6 Å. The diffusion of the Al cations therefore limited the cation-exchange process. The addition of NH4+ to the pillaring solution decreased the amount of Al fixed by the clay from 31 (no NH4+ to 26 wt. % (NH4+/Al = 10), but increased slightly the microporous volume of the resulting pillared material from 0.13 to 0.14 ml/g. The competition between NH4+ and Al-hydroxy cations for ion-exchange sites forced the Al species into the interlayer space and increased the homogeneity of the resulting pillared material. The influence of particle size on the amount of Al exchanged was then reduced. After calcination in air at 700°C the pillared Wyoming clay retained a microporous volume of 0.09 ml/g if no NH4+ was added, compared with 0.11 ml/g for a NH4+/Al ratio of 10. The Fe content of the clay affected the thermal stability of pillared clays at 800°C: for two samples prepared by competitive ion exchange (NH4+/Al = 10) the microporous volume increased from 0.06 ml/g for 6.4 wt. % Fe2O3 to 0.08 ml/g for 0.5 wt. % Fe2O3. The acidity of the pillared clay was determined by calorimetric adsorption of ammonia at 150°C, on samples calcined at 500°C. Pillared montmorillonite prepared using noncompetitive intercalation showed a weak acid strength: most sites adsorbed ammonia with an enthalpy of 65 kJ/mole. The intercalation of the same original clay using competitive ion exchange yielded a solid that possessed both weak (heat = 60 kJ/mole) and strong (120 kJ/mole) acid sties. Competitive ion exchange appears to be a simple means of preparation of large quantities of pillared clays of reasonable thermal stability and higher acidity than those obtained by conventional methods.

A kaolinite-pyridine intercalation compound was prepared using hydrated kaolinite as an intermediate. Hydrated kaolinite having a basal spacing of 10 Å was treated with pyridine to form a well-ordered intercalation compound having a basal spacing of 12.0 Å. Infrared spectroscopy indicated the presence of hydrogen bonding between the hydroxyls of the kaolinite and the pyridine. 29Si nuclear magnetic resonance spectroscopy with cross polarization and magic-angle spinning revealed that intercalated pyridine affected the environment of silicon. The mono-substituted pyridine derivatives were also intercalated with hydrated kaolinite. On the basis of the basal spacings of the intercalation compounds and the stabilities of the derivatives between the layers, the pyridine appeared to be in an approximately perpendicular position, with the nitrogen facing the gibbsitic sheets.

A combination of X-ray diffraction, infrared, and chemical data has established that the ion exchange of vermiculite with singly charged benzidine cations in an aqueous solution at pH 1.6 results in a black, highly ordered benzidine-vermiculite intercalate. The intercalate has a basal spacing of 19.25 Å and a primitive unit cell with “a” and “b” edges parallel and equal to those of vermiculite. The number of benzidine molecules per cell is equal to its electric charge. In this structure the benzidine molecules are steeply inclined to the silicate surfaces and close-packed within domains. The domains contain alternating rows of benzidine cations; from row to row the planes are either approximately parallel or perpendicular to the (120) plane, but along any one row the planes of the aromatic rings are parallel to each other. Hydrogen bonding operates between amine nitrogens and surface oxygens.

Dealumination of vermiculite was carried out using (NH4)2SiF6 solutions. The dealuminated products were studied by high-resolution solid state 29Si and 27Al nuclear magnetic resonance. A decrease in the cation-exchange capacity (CEC) resulted from the partial removal of Al from the tetrahedral layer, which decreased the framework negative charge, and from the partial replacement of Mg by Al in the octahedral layer, which increased its positive charge contribution. The lowest CEC was obtained by swelling the structure with butyl-ammonium prior to the reaction with (NH4)2SiF6. Thus, CECs in the range observed for beidellite were measured; however, the lowest (Al/Si)IV ratio was still more than twice as high as in beidellite. In addition, the dealumination reaction yielded noncrystalline silica as a by-product.

In contact with a solution of Al hydroxypolymer (Al13), the dealuminated vermiculite showed no 18-Å reflection characteristic of Al13-intercalated smectite; instead it showed an ill-defined interstratification. For some samples, however, a significant increase in the specific surface area (as much as 230 m2/g) was observed, suggesting that an intercalation of Al moieties did occur. The 27Al resonance spectra of the intercalated structure showed at least two components in octahedral coordination. On thermal activation, a resonance line attributable to pentacoordinated Al was observed.

A kaolinite-polymer intercalation complex was apparently formed for the first time by the polymerization of acrylonitrile between the kaolinite layers. A kaolinite-ammonium acetate intercalation complex was dispersed in acrylonitrile monomer. The monomer was apparently incorporated between the layers by displacing intercalated ammonium acetate. After the removal of excess monomer, the intercalation complex was heated to cause polymerization. The resulting kaolinite-polyacrylonitrile (PAN) intercalate showed a basal spacing of ∼ 13–14 Å. On heating the complex at 220°C for 1 hr in air, the spacing decreased slightly. The hydrogen bond between the hydroxyls of kaolinite and probably the C≡N group of PAN was not affected after heating at 220°C. Even after heating at 400°C, the layers expanded. Because the starting kaolinite-ammonium acetate intercalation complex decomposed at a much lower temperature, these observations strongly suggest the presence of PAN between the layers.

The adsorption and degradation on montmorillonite of s-triazine, the parent compound of a major group of triazine-based herbicides, were studied by Fourier-transform infrared spectroscopy. The original s-triazine appeared to hydrolyze with residual bound water in montmorillonite at 20°C to produce formamide, which formed an intercalate with the clay. A mechanism for the conversion of s-triazine to formamide was proposed which does not support earlier reports that formic acid and ammonia are the reaction products. The infrared spectrum of the formamide-Na-montmorillonite intercalate suggests that formamide reacted with the exchangeable Na cation and that the NH2 group hydrogen bonded with the clay. Assuming the intercalated formamide molecule to be planar, the molecular plane was found to be inclined at ~33° with respect to the plane of the silicate sheet. C-N and C-O bonds were also found to be tilted at the same angle with respect to the clay surface. The proposed orientation is in good agreement with the measured value of d(001) for the formamide-Na-montmorillonite complex. The proposed model of the formamide-montmorillonite complex serves as a basis for comparison of other clay-amide complexes that are important in protein-clay interactions.

X-ray diffraction patterns of oriented films of montmorillonite containing enantiomeric tris(2,2′-bipyridyl) ruthenium(II) chloride (Ru(bpy)22+) show a peak corresponding to basal spacings of approximately 27 Å. This peak is absent from the X-ray patterns of montmorillonite films containing racemic cations. A basal spacing of 27 Å is consistent with the adsorption of 2 layers of the enantiomeric cations in each interlayer space. Under the same condition only one layer of the racemic cation was intercalated (basal spacings of 17.9 Å). These results are in accord with previous reports that montmorillonite can adsorb more of the optical isomers than of the racemic mixture of Ru(bpy)32+. Addition of NaCl to the mixtures resulted in an increase in the level of adsorption of the racemic cations and in the appearance of a peak at 27 Å in the X-ray pattern.