Intercalation clays

The time (days) to 50% loss were sand (17) > kaolinite (4) > soil (3) > halloysite (1) > montmorillonite(< 0.1). The rate was most rapid for the solid media exhibiting extreme pH values (halloysite, montmorillonite), and highest for the intercalating clay, montmorillonite. The observed recovery from the soil sample (Te Kowhai) was intermediate to... 

These results indicate limited persistence of M2D—C3—O—(EO ) — CH3 in the parent form in typical soil and aqueous environments. In general, the rates of loss observed in the presence of solid media show a dependence on pH as is observed in aqueous media, with lower recoveries in acidic and alkaline pH media, and in the presence of charged and intercalating clay minerals. 

A mixture of intercalating clays is generally found in the subsurface. Interstratification of kaolinite and smectite has been reported in some cases (e.g., Schultz et al. 1971 Lee et al. 1975a, 1975b Yerima et al. 1985). This fact is reflected in an XRD... 

Reduction of metal oxides, intercalated between the 72 clay layers (pillared clays), led to metal-intercalated clay nanocomposites... 

A portion of the wet sol-intercalated clay was mixed with a surfactant of quaternary ammonium salts [CH3(CH2)n-i N(CH3)3Br] by stirring for 2 hours. 15.75 mmol of surfactant was added to each gram of the starting bentonite clay. The resultant mixture of clay and surfactant was transferred into an autoclave and kept in an oven at 100°C for 3 days. The wet cake was washed with water to Cl ions free and the solid was recovered by filtration. The solid was dried in room temperature and calcined at 773 K. for 4 h. The calcined products were labeled as sol-PILB-Cn, where n denotes the number of carbon atoms in the alkyl chain of the surfactants used. Four samples were prepared sol-PILB-C12, -C14, -C16 and -C18. 

The relatively small size of the pillars and the relatively low long-range ordering of intercalated clays exclude many surface and crystallographic techniques as suitable means of characterization. The present study is the first attempt to obtain interatomic distances in these systems from EXAFS data. Our results clearly show the utility of this method for local structural analysis of these clay materials. The interatomic distances obtained for chromia-pillared montmorillonite suggest similarities between the structure of the pillars and the structure of Cr203 (22). This result is in agreement... 

The resulting intercalated clays were dried in air at 323 K for 16 h and then calcined at 773 K for 4 h in order to obtain the alumina-pillared clays. The solids are designated hereafter as (BAsap-Al)T, where BAsap refers to the starting clay used. The following letter indicates the aluminium polycation used (Al, or AI13) and T the calcination temperature. In the case of the Alheid, polycation, the Al/heidi mole ratio used (2 or 3) is also included ((BAsap-Al/,, , -2) and (BAsap-Al/,e,, -3)773, respectively). 

Galameau et al. [81] used a similar approach to design porous clay heterostructures. They intercalated layered fluorohectorite by CjgTMA cations followed by treatment in a solution of neutral amine and TEOS, then drying and calcination. In brief, the authors proposed that the interlayer galleries of the intercalated clay are further swollen by the amine followed by insertion of TEOS, formation of rod-like micelles and silica polymerization. 

In order to improve the textural properties of particle-clay nanohybrids, bulky organic cations are intercalated as a kind of template into particle-intercalated clays before stabilization procedures. Intercalation of the organic cations results in the removal of some of the intercalated nanoparticles and/or in their rearrangement. Subsequent calcination leads to formation of additional pore space that is highly correlated to the geometry and size of the templates. This technique allows fine tuning of textural properties in the preparation of particle-clay nanohybrids. The clay nanohybrids intercalated with metals, oxides, and complexes have a broad range of applications. In particular, metal oxide particle-pillared clays have excellent potentials as catalysts, catalyst supports, selective adsorbents, etc. " ... 

Figure 16.24 shows the schematic representation of dispersed clay particles in a polymer matrix. Conventionally dispersed clay has aggregated layers in face-to-face form. Intercalated clay composites have one or more layers of polymer inserted into the clay host gallery. Exfoliated polymer/clay nanocomposites have low clay content (lower than intercalated clay composites which have clay content -50%). It was found that 1 wt% exfoliated clay such as hectorite, montmorillonite, or fluorohectorite increases the tensile modulus of epoxy resin by 50-65%. ... 

Specific surface area and microporous volume data for intercalated clays prepared with different zirconium concentrations. 

When the Zr concentration and the S04 Zr ratio increase, the formation of a polymeric phase is accentuated. For low S04 Zr ratio, the pillars in the intercalated clay fraction consist of non sulfated polycations. But when the zirconium concentration is low (0.025 mol/L) and the S04 Zr ratio is high, the intercalation of sulfated polycations occurs. These preparation conditions give a solid with a high textural thermal stability. Sulfate ions linked to Zr-pillars seem to be more stable than those incorporated in the polymeric phase. Those sulfate ions dispersed in the solid could generate an interesting catalytic behaviour that merits further study. 

Conducting polymers such as PANl- or PPY-intercalated clay-type minerals are another type of ER particle material. Kim et al. synthesized PPY-intercalated montmorillonite nanocomposites through inverted emulsion pathway polymerization, and characterized its ER effect under an electric field [38]. The nanocomposites showed not only a typical ER behavior under electric fields but also the existence of a critical electrical field when the yield stress was plotted as a function of the electric field. 

Eberl DD, Nuesch R, Sucha V, Tsipursky S (1998) Measurement of fundamental illite particle thicknesses by X-ray diffraction using PVP-10 intercalation. Clays Clay Minerals 46 89-97 Eberl DD, Srodon J (1988) Ostwald ripening and interparticle-diffraction effects from illite crystals. Am Mineral 73 1335-1345... 

A breakdown of the mineral compositions of a typical oil sand, overburden clay layers in the McMurray Formation, and the MFT are given in Figure 10. The figure shows that kaolinite and illite dominate the clay fraction in all of these materials, with smectites generally found only in the overburden and in intercalated clay lenses in the oil sands. The amounts and types of clay minerals found in tailings ponds vary considerably, but assays of tailings pond MFT show mostly kaolinite and illite (30-32). Montmorillonite has been reported in the Suncor MFT... 

Zerda, AS, Lesser, AJ. 2001. Intercalated clay nanocomposites Morphology, mechanics, and fracture behavior. JPolym Sci 39 1137-1146. 

Since nanoparticles in PNC are orders of magnitude smaller than conventional reinforcements, the models developed for composites are not applicable to nanocomposites. However, development of a universal model for PNC is challenging since the shape, size, and dispersion of the nanoparticles vary widely from one system to another. On the one hand, exfoliated clay provides vast surface areas of solid particles (ca. 800 m /g) with a large aspect ratio that adsorb and solidify a substantial amount of the matrix polymer, but on the other hand, the mesoscale intercalated clay stacks have a much smaller specific surface area and small aspect ratio. However, in both these cases the particle-particle and particle-matrix interactions are much more important than in conventional composites, affecting the rheological and mechanical behavior. Thus, the PNC models must include the thermodynamic interactions, often neglected for standard composites. 

Hsieh et al. [2004] investigated the mechanical and fiow behavior of polycarbonate (PC)-based CPNC, prepared in a corotating TSE with 1.5 to 5 wt% C25A. The rubbery plateau modulus of PNC with finely dispersed intercalated clay decreased significantly. PNC with 5 wt% clay had Tg lower by about 10°C than neat PC, traced to the degradative reduction of its A/w by 43%. 

Fig. 30 (a) Representative TEM image of exfoUated-intercalated clay in a poly(ethyl acrylate) matrix containing 5 wt% of clay. Dependence of mechanical (b), thermal (c), and permeation (d) properties with clay loading. Adapted from [256] with permission of Wiley Periodicals... 

Choudhaiy, S., Sengwa, R. J. (2014). Intercalated clay structures and amorphous behavior of solution cast and melt pressed poly(ethylene oxlde)-clay nanocomposites,/ Appl. Polym. Set, 131(4), DOI 10.1002/ app.39898. 

---