Montmorillonite modification

Staunton, S. and Quiquampoix, H. (1994). Adsorption and conformation of bovine serum albumin on montmorillonite modification of the balance between hydrophobic and electrostatic interactions by protein methylation and pH variation. Journal of Colloid and Interface Science 155, 89-94. 

G. D. Boss and E. O. Stejskal, Restricted, anisotropic diffusion and anisotropic nuclear spin relaxation of protons in hydrated vermiculite crystals, J. Colloid Interface Sci. 26 271 (1968). S. Olejnik and J. W. White, Thin layers of water in vermiculites and montmorillonites Modification of water diffusion. Nature Phys. Sci. 236 15 (1972). J. Hougardy, J. M. Serratosa, W. Stone, and H. van Olphen, Interlayer water in vermiculite Thermodynamic properties, packing density, nuclear pulse resonance, and infrared absorption, Spec. Disc. Faraday Soc. 1 187 (1970). 

We alluded earlier to the variety of structural modifications which may he observed in sheet silicates. Clearly it is a matter of considerable in jortance to he able to determine if, for example, the aluminium content within a clay arises p a ely from octahedral substitution (as in montmorillonite) or whether there is some tetrahedral component (as in heidellite). a1 MASNMR readily provides the necessary answers. Figvire 1 illustrates the a1 spectrum for a synthetic heidellite material with Na as charge balancing cation. Aluminium in two distinct chemical environments is observed, with chemical shifts corresponding to octahedrally and tetrahedrally co-ordinated aluminium. 

The dispersion and solid-state ion exchange of ZnCl2 on to the surface of NaY zeolite by use of microwave irradiation [17] and modification of the surface of active carbon as catalyst support by means of microwave induced treatment have also been reported [18]. The ion-exchange reactions of both cationic (montmorillonites) and anionic clays (layered double hydroxides) were greatly accelerated under conditions of microwave heating compared with other techniques currently available [19.]... 

A small increase of the (d 001) basal spacing is observed for the Li containing Zr pillared clays. However, the thermal stability of these solids drastically decrease. At high temperature, the collapse of the strucutre is also supported by the decrease of the surface area which is, at 700°C, almost identical to those measured for the montmorillonite. Different hypothesis may be proposed to explain the increase of the interlayer distance at low temperature (i) a better polymerization of the intercalated complex (ii) a modification of the distribution of the pillars (iii) a lower interaction between the pillar and the silica layer. The first hypothesis may easily be eliminated since the small variation of the height of the pillars (less than 1 A) cannot be explained by structural changes of the... 

Sodium bentonite with a cation exchange capacity (CEC) of 75 meq/100 g of clay, supplied by Commercial Minerals Ltd., Australia, was used as starting clay material, to prepare samples for SCD and surfactant treatments. Besides, sodium montmorillonite (Kunipia G), from Kunimine Industrial Company, Japan, was used as the starting clay for samples of pore opening modification. CEC of this clay is 100 meq/100 g of clay. 

Recently, interest in clays as acidic catalysts has been quickened by the reported high catalytic activity of a synthetic mica-montmorillonite clay and its nickel-containing analogs. Wright et al. (247) have described the structure, thermal modification and surface acidity of the clay, which they designated SMM for synthetic mica-montmorillonite. 

Gianfreda and Bollag (1994) investigated the behavior of laccase and peroxidase in the presence of a montmorillonite, a kaolinite, and a silt loam soil. They observed considerable variation in the retained activities of the two enzymes immobilized on the different supports as well as variation in the amount of each enzyme sorbed (Table 2.10). Interestingly enough, laccase immobilized on montmorillonite showed a higher specific activity (118%) than that of the free enzyme. This may be attributed to the steric modification of the immobilized enzyme or possibly due to the catalytic ability of montmorillonite itself. Their studies showed that the performance of these enzymes is significantly affected by soil mineral colloids. 

Diagenetic modification of expandable clay during burial is an important source of mixed-layer illite-montmorillonite. With increasing depth of burial and increasing temperature the proportion of contracted 10 A layers systematically increases. From about 50°C— 100°C the contracted layers are distributed randomly. At higher temperatures only a few additional layers are contracted but the interlayering becomes more ordered (Perry and Hower, 1970 Weaver and Beck, 1971a). The final product, 7 3 to 8 2, is relatively stable and persists until temperatures on the order of 200°C— 220° C are reached. 

CIL is unavoidable when nanodispersion of any other nanofiller, such as clay or carbon nanotube (CNT) is considered [17,18], Various types of cationic surfactants in the case of montmorillonite (MMT) and reactive interface modifications in the case of CNT have been introduced to ensure... 

Wang, Z.M. Nakajima, H. Manias, E. Chung, T.C. Exfoliated PP/clay nanocomposites using ammonium-terminated PP as the organic modification montmorillonite. Macromolecules 2003, 36, 8919. 

Illite and montmorillonite are similar in structure and differ slightly from kaolinite in this regard. The first two are composed of two silicon-oxygen layers per octahedral layer containing iron, magnesium and aluminum and in kaolinite the ratio of tetrahedral and octahedral layers is 1. In clays thermal modification occurs at lower temperature than silica because the bonds formed between the Al, Fe, and Mg atoms and oxygen are weaker than the Si-0 bonds. 

Polymer clay nanocomposites have, for some time now, been the subject of extensive research into improving the properties of various matrices and clay types. It has been shown repeatedly that with the addition of organically modified clay to a polymer matrix, either in-situ (1) or by melt compounding (2), exfoliation of the clay platelets leads to vast improvements in fire retardation (2), gas barrier (4) and mechanical properties (5, 6) of nanocomposite materials, without significant increases in density or brittleness (7). There have been some studies on the effect of clay modification and melt processing conditions on the exfoliation in these nanocomposites as well as various studies focusing on their crystallisation behaviour (7-10). Polyamide-6 (PA-6)/montmorillonite (MMT) nanocomposites are the most widely studied polymer/clay system, however a systematic study relating the structure of the clay modification cation to the properties of the composite has yet to be reported. 

The present study makes an attempt to increase mesoporosity within the pillared structure of montmorillonite and to study the catalytic property of the resulting material. Enhancement of mesoporous areas has been observed in a smectite seunple pillared by aluminium polyoxy cations by chemical modification in presence of varied amounts of a nonionic surfactant. The effeet of the enhaneement in mesoporous areas on the pillar density and the deaetivation of the pillared materials in a typical alkylation reaction has been studied. 

Chemical modification with different amounts of tween-80, a nonionic surfactant, was foimd to enhance the mesoporous area in pillared montmorillonite samples. Deactivation of the modified clays in the vapour phase catalysis of alkylation of toluene by methanol showed that the pillar density and the rate of deactivation could be controlled by the amount of surfactant used during the preparation of pillared samples. Presence of surfactant within the gallery affects the distribution of pillars perhaps during washing and dehydration. This offers a method to suppress deactivation in pillared samples to catalyze organic reactions. 

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