Ion diffusion in diffuse double layer: Dynamic distribution and exchange equilibrium. (6461)
Authors:
H. Li - University of California, Riverside L. Wu* - University of California, Riverside
Abstract:
Ion diffusion and exchange in soil are usually treated as two independent processes.
Ion diffusion is described by Fick’s first and second laws without considering the influence of electrical field, while ion exchange is described by adsorption and desorption processes without considering the dynamic nature of ion distribution in the diffuse double layer (DDL). There are two ways to deal with the exchange equilibrium: (1) treat the ion exchange process as a chemical reaction; or (2) treat it as a physical chemical process, thus allowing the equilibrium equations of ion exchange based on the theory of DDL and the theory of Donnan equilibrium to be applied. Based on the equations developed earlier for describing ion diffusion in electric field, this research adapted a new approach to describe the physical and chemical ion exchange process. In this approach, ion exchange was treated as a mutual diffusion of the exchanging ions driven by their activity gradient in an electric field, and new equilibrium equations of ion exchange in different types of electrolyte systems were established. When the exchanging ions are treated as point charges, the new equations naturally reduce to their classic forms. Based on the new theory, the dynamic distribution model of the ions in DDL during the ion exchange process was developed. This model naturally reduces to the Boltzmann equation when the ion exchange reaches equilibrium.
Speaker Information: Laosheng Wu, University of California, Riverside, 2208
Geology Building Dept. of Environmental Sciences University of California, Riverside, CA 92521; Phone: (909)827-4664; E-mail: [email protected]
Session Information: Monday, November 1, 2004, 5:00 PM-6:00 PM Presentation Start: 5:00 PM (Poster Board Number: 2810)
Keywords: Ion diffusion; Diffuse double layer; dynamic; exchange equilibrium
