DIFFUSE DOUBLE-LAYER EQUATIONS IN SI UNITS

Clay particles are usually treated as lyophobic colloids and, thus, colloid chemistry provides a means for description of interactions in a clay-water-electrolyte system. The Stern-Gouy-Chapman theory of diffuse double layer has been applied to the behavior of clays with varying degrees of success. In most textbooks, the equations describing the diffuse double layer are given in electrostatic units. However, it is very confusing for researchers of different disciplines to communicate this way, as the existing equations are not even in compliance with the counterparts in electrical engineering. Moreover, it complicates double-layer computations when coupled flows are involved, i.e., one type of flow is induced by another type of force. These problems become apparent as the amount of research in hazardous waste management and site remediation grows. Hence, it is worthwhile to redevelop these equations using the SI system to eliminate these ambiguities and a redundant conversion factor. Moreover, it is shown that the SI equations can be obtained very conveniently by replacing the dielectric constant term in esu equations by the product of 4π and the permittivity of the medium. © ASCE.