Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Srodon, J. Articles by McCarty, D. K. Search for Related Content GeoRef GeoRef Citation

SURFACE AREA AND LAYER CHARGE OF SMECTITE FROM CEC AND EGME/H₂O-RETENTION MEASUREMENTS

Jan rodo¹ and Douglas K. McCarty²

¹ Institute of Geological Sciences PAN, Senacka 1, 31002 Krakow, Poland
² Chevron ETC, 3901 Briarpark, Houston, TX 77042, USA

^* E-mail address of corresponding author: ndsrodon{at}cyf-kr.edu.pl

The total specific surface area (TSSA) and smectitic layer charge (Q_s) 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_s measurement techniques based on cation exchange capacity (CEC), H₂O 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 H₂O from smectite on heating, and to introduce a correction for H₂O 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_s 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 H₂O coverage; (2) using mean EGME coverage; and (3) using a combination of H₂O 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 H₂O and EGME coverage on layer charge. The study demonstrates that Ca²⁺-smectite samples at 47% RH have H₂O contents corresponding to 88–107% of the theoretical mass of a monolayer and offers an explanation of this variation.

Key Words: CEC • Charge Density • EGME • Layer Charge • Smectite • Specific Surface Area • Water Sorption

This article has been cited by other articles:

				R. Dohrmann and S. Kaufhold THREE NEW, QUICK CEC METHODS FOR DETERMINING THE AMOUNTS OF EXCHANGEABLE CALCIUM CATIONS IN CALCAREOUS CLAYS Clays and Clay Minerals, June 1, 2009; 57(3): 338 - 352. [Abstract] [Full Text] [PDF]