Effect of Water Content on Clay Pore Size using an Atomic Force Microscope

Clays and its composites have been widely used in the past as a secondary containment wall for underground storage tanks and landfills. The underground storage tanks are used commonly to store gasoline and other organic chemicals, both in the industry and the commercial market. Recent studies have shown that these secondary containment walls are failing. Gasoline and many other organic contaminants pass through clay liners without much effort. This study attempts to evaluate the changes occurring in the interactions between water molecules and clay particles at a microscopic level, using an atomic force microscope, for varying levels of water content. The pore size changes occurring in the clay particle lattice have a profound effect on the permeability of clay. The results show that the clay pore diameters reduce exponentially as the water content increases. This change of pore size can be attributed to the reduction in the size of the diffuse double layer and more extensive hydrogen bonds between clay particles and bipolar water molecules. Due to sample preparation difficulties, however, the pore diameters were obtained when the clay was dry, while interest for underground storage tank containment layer is for wet conditions.