Clay/water interface and its role in the environment

Abstract

Data are presented to show that the surfaces of a common clay mineral, montmorillonite, modify the properties of the nearby water to a depth of at least 3.5 nm and that the value of every water property depends exponentially on t, the thickness of the films of adsorbed water, but is independent of the character of the surfaces. The viscosity and yield point are among the properties of the water that are modified. A modification of either of these properties has a commensurate effect on the flow of water between adjacent surfaces. Data are also presented to show that the surface-induced modification of the water is responsible for the swelling of the clay mineral and affects its ability to adsorb solutes. The swelling of clay reduces the permeability of the soil and the adsorption of solutes by the clay reduces their mobility. Thus, clay-water interaction has a significant impact on the convective and diffusive transport of pollutants through the soil.