(409e) Volume Averaging Study of Surface Transport in Charged Porous Media

Surface transport occurs in a variety of physical processes of interest in many fields: engineering, physics, geology, colloidal science, and biology. Many times, these phenomena are not well understood and, therefore, not considered in the treatment of transport processes. There are few studies of surface transport in charged porous media, when an electric field is externally applied.

A new model that describes ion transport by bulk and surface transport inside charged porous carbon electrodes is proposed to simulate the CDI process. A general treatment of bulk and surface transport processes is presented in terms of the method of volume
averaging. In addition to the spatial-averaging theorem, the analysis requires the surface-averaging theorem plus a closure scheme. The closure problem is formulated
and overall effective diffusivities are calculated using Chang’s unit cells.  The influence of surface migration terms is also discussed. The derived transport equations lead to well-known results in the case of non-charged materials.