Surface area and layer charge of smectite from CEC and EGME/H2O-retention measurements
Środoń, Jan (Institute of Geological Sciences PAN)
McCarty, Douglas K. (Chevron ETC)

Fecha:	2008
Resumen:	The total specific surface area (TSSA) and smectitic layer charge (Q) calculated from the structural formulae and unit-cell dimensions of 12 pure smectite samples were used as a reference in the design and evaluation of TSSA and Q measurement techniques based on cation exchange capacity (CEC), HO retention at 47% RH, and ethylene glycol monoethyl ether (EGME) retention. A thermogravimetric analysis-mass spectrometry (TGA-MS) technique was used to study the release of HO from smectite on heating, and to introduce a correction for HO remaining in the smectite after heating to 110°C, because the sample weight at this temperature has been used routinely as a reference in CEC and EGME sorption measurements. A temperature of 200°C was found to be the optimum reference for such measurements. A good agreement between Q from the structural formula and from CEC was obtained when this correction was applied. The TSSA of smectite was measured with similar accuracy (mean error of ±5-7%) by three techniques: (1) using mean HO coverage; (2) using mean EGME coverage; and (3) using a combination of HO coverage and CEC. A reduction of the mean error from 5-7% to 4% can be obtained by averaging these measurements, and a further reduction to 3% by introducing corrections for the dependence of HO and EGME coverage on layer charge. The study demonstrates that Ca-smectite samples at 47% RH have HO contents corresponding to 88-107% of the theoretical mass of a monolayer and offers an explanation of this variation.
Derechos:	Tots els drets reservats.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	CEC ; Charge Density ; EGME ; Layer Charge ; Smectite ; Specific Surface Area ; Water Sorption
Publicado en:	Clays and Clay Minerals, Vol. 56, Núm. 2 (2008) , p. 155-174, ISSN 1552-8367

DOI: 10.1346/CCMN.2008.0560203

20 p, 288.5 KB  Acceso restringido a la UAB

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