Characterization of montmorillonite surfaces after modification by organosilane.
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{sub 18}H{sub 37}SiCl{sub 3}) and octadecyltrimethoxysilane [C{sub 18}H{sub 37}Si(OMe){sub 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 C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 3} resulted in hydrophobic coating that acts like a 'cage' around the clay particles to limit diffusion. Basal spacings of the organic modified clays remain at {approx}15 {angstrom} upon heating to 400{sup o}C in N{sub 2}, whereas those of unmodified clays collapse to {approx}10 {angstrom}. 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 C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 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.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 942927
- Report Number(s):
- ANL/CHM/JA-36012; TRN: US200923%%608
- Journal Information:
- Clays Clay Miner., Vol. 49, Issue 2 ; Apr. 2001; ISSN 0009-8604
- Country of Publication:
- United States
- Language:
- ENGLISH
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