HR: 0800h
AN: H31D-0418    [Abstracts]
TI: The Effects of Moisture on the Surface and Pore Areas of Kaolinite, Montmorillonite and Silica Gel
AU: * Monterrosa, A
EM: atmonterrosa@yahoo.com
AF: California State University Los Angeles, Department of Civil Engineering 5151 State University Drive, Los Angeles, CA 90032 United States
AB: A key factor in the uptake and release of contaminants in soils is the amount of water adsorbed on the surfaces of the soil particles. It is hypothesized that the surface and pore areas of porous solids will decrease because of the presence of this adsorbed water layer. In our experiments, we incubated four different solids (2 silica gels, kaolinite, and montmorillonite) in three different controlled environments (relative humidity (RH) values of 16%, 76%, and 86%) at ambient temperatures for over 440 days. Our results indicate that moisture significantly affects the surface areas of all solids except kaolinite. The surface areas of one of the silica gel samples incubated at 16%, 76%, and 86% were 271.1 m$^{2}$/g, 237.5 m$^{2}$/g, and 218.1 m$^{2}$/g, respectively. Contrary to this, the surface areas of montmorrillonite increased with increasing RH because of the expansion of the clay layers. However, long-term incubation of montmorrillonite at 86% humidity resulted in a decrease in surface areas (surface areas of montmorrillonite at 76% RH increase from 2.95 to 7.10 m$^{2}$/g while at 86% RH, they increase to 6.03 m$^{2}$/g)), probably because more moisture was available at 86% RH to condense inside the pores and between the layers of the clay, reducing surface areas. This study is important because it will allow us to quantify the effects of moisture on the physical properties of particles and, hence improve our current understanding of contaminant distribution and fate in soils. These results are also important because they enhance our understanding of the swelling of clays such as montmorrillonite.
DE: 1832 Groundwater transport
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting