Characterization of Montmorillonite Surfaces After Modification by Organosilane

Abstract

Abstract--X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), surface area measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to examine the surface properties of organosilane-modified smectite-type aluminosilicate clays. Organic modified clays derived from the reactions of montmorillonite (containing 93-95% montmorillonite from a bentonite, <1% quartz, and 4-6% opal CT) with octadecyltrichlorosilane (C~sH37SiCI3) and octadecyltrimethoxysilane [CIsH37Si(OMe)3] are highly hydrophobic. Surface loadings of the modified clays depend on the organosilane and the solvent, and they range from 10 to 25 wt. %. The organic species are probably adsorbed to the outer surfaces and bound to the edges of the clay via condensation with edge-OH groups.Encapsulation of montmorillonite with CIsH37SiC13 and ClgH37Si(OMe)3 resulted in a hydrophobic coating that acts like a "cage" around the clay particles to limit diffusion. Basal spacings of the organic modified claysoremain at --15 A upon heating to 400~ in N2, whereas those of unmodified clays collapse to --10 A. A considerable reduction in surface area (by 75-90%) for organic modified clays is observed, which is consistent with the existence of a surface coating. The solvent used can affect the amount of organic silane coated on the clay particles, whereas the difference between the products prepared using C18H37SIC13 and ClsH37Si(OMe)3 in the same solvent is relatively small. The carbon and oxygen K-edge NEXAFS spectroscopy of the modified montmorillonite surfaces showed that surface coatings on the outside of the clay particles exist. The encapsulating system may allow for economical remediation and storage of hazardous materials.

Adsorption of phenol on natural clay

“…Natural and activated clay were considered fast because of a rapid increase of adsorbates adsorbed were occurred at the 180 min. Previous findings on the adsorption of phenolic compounds by various clay-based adsorbents have shown a wide range of adsorption time (Song and Sandi 2001).…”

Drastic increase in catalyst productivity of nanoclay-supported CVD-grown carbon nanotubes by organo-modification

“…Adsorption of intercalant (organo-cations) on clay caused a constriction of the pore channels owing to attachment of the intercalant moieties to the internal framework surfaces. Moreover, organic intercalant coated the outer surface of the nanoclay make it inaccessible to nitrogen molecules (Song and Sandí, 2001). This can lead to a substantial decrease in the SSA of OC compared to that of the pristine clay (Krishna et al, 2000).…”

Silylation of montmorillonite surfaces: Dependence on solvent nature

“…The basal spacing of the silylated products strongly depended on the configuration of the silane used [17], the loaded silane amount in the interlayer spaces [18] and the interactions among silane molecules (e.g., intermolecular hydrogen bonding) and between clay mineral and special group of silane (e.g., -NH 2 group) [20]. The chemical nature of the solvents used in silylation reaction has significant influences on the amount and distribution of the grafted silanes and the structure of the silylated products [16,21,22]. Shanmugharaj et al reported that the surface energy of the solvents showed a significant effect on the average basal spacing of the grafted products [16].…”