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United States Department of Agriculture

Agricultural Research Service

Title: Ranges of Bound Water Properties Associated with a Smectite Clay

Authors
item Logsdon, Sally
item Laird, David

Submitted to: Electromagnetic Wave Interaction with Water and Moist Substances Proceeding
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 2003
Publication Date: March 26, 2003
Citation: LOGSDON, S.D., LAIRD, D.A. RANGES OF BOUND WATER PROPERTIES ASSOCIATED WITH A SMECTITE CLAY. ELECTROMAGNETIC WAVE INTERACTION WITH WATER AND MOIST SUBSTANCES PROCEEDING. 2003. P. 101-108.

Technical Abstract: Dielectric spectroscopy has been used to characterize various colloids with constant potential surfaces. The objective of this study is to utilize dielectric and electrical conductivity spectroscopy to study a humidified Ca -- Wyoming bentonite, a clay mineral with variable potential surfaces due to the dominance of permanent charge sites. Before the analysis, the samples were humidified to four different levels (54 to near 100% relative humidity). For each humidity level, duplicate samples of humidified clay were each packed into a coaxial cell. The dielectric and electrical conductivity spectra were measured using a vector network analyzer for frequencies ranging from 300 kHz to 3 GHz at each of six temperatures between 10 and 35 degrees C. Dielectric relaxations were fit to a Cole-Cole empirical equation and relaxation free energies and viscosities of the adsorbed water were calculated from the relaxation times. The dielectric relaxations for the hydrated smectite systems were very broad with exponent values around 0.5. Neither the real component of the electrical conductivity nor the real component of the dielectric showed a static value at the low frequency end of the spectra. The calculated viscosities were orders of magnitude larger than for free water. The log-log plot of the complex dielectric indicated a trend toward the low frequency dispersion, but the slopes were not identical for the real and imaginary components. All of the slopes were between 0.8 and 1.0 except for one sample at the low humidity (54%) in which the slope was < 0.8. The usual explanation for the low frequency dispersion in humidified samples is proton hopping within clusters of hydrogen bonds. For the humidified Ca-smectite, a wide range of water interactions are occurring.

Last Modified: 10/1/2014
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