Interlayer and Intercalation Complexes of Clay Minerals

The role of charcoal on DTA curves of organo-clay complexes: an overview

A one-step, direct method is described for the creation of synthetic smectite clays grafted with organics on the interlayer surfaces using an organotrialkoxysilane as the silica source. The silane ...

Use of Organo- and Alkoxysilanes in the Synthesis of Grafted and Pristine Clays

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 (C18H37SiCl3) and octadecyltrimethoxysilane [C18H37Si(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 C18H37SiCl3 and C18H37Si(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 clays remain at ∼15 A upon heating to 400°C 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 C18H37SiCl3 and C18H37Si(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.

Characterization of montmorillonite surfaces after modification by organosilane

Mica-type layer-silicates such as montmorillonite and vermiculite are capable of exchanging their cations for other (including organic) cations, just like the zeolites. These derivatives swell in a variety of liquids. This paper presents a survey of the structures of organic derivatives of mica-type layer-silicates and illustrates some possibilities for their industrial utilization.

Organic Derivatives of Mica‐type Layer‐Silicates

Die inneren und ausseren Oberflachen der kolloiden Tonmineralien sind reich an reaktionsfahigen Hydroxylgruppen. Es gelingt, unter weitgehender Erhaltung des Kristallgitters, kovalent haftende, organische Gruppen in die Montmorillonitoberflachen einzubauen. Dadurch werden die Eigenschaften des Tons grundlegend verandert. Bisher wurden vor allem Ester gewonnen, und zwar einerseits durch direkte Einwirkung von Senfgas und Propylenoxyd auf den Ton, andererseits durch Einwirkung verschiedener Alkohole auf Montmorillonitchlorid. Aus dem Tonchlorid und Tonester liessen sich durch Reaktion mit Athylendiamin stickstoffhaltige Derivate mit Ampholytcharakter gewinnen.

G. Huber

Papers

Organische Derivate von Tonmineralien