Boundary-Layer Analysis of Polarization in Electrodialysis in a Two-Dimensional Laminar Flow

Abstract

The problem of ion transfer in the fluid phase of an electrodialysis stack with parallel flow is considered for two extreme cases: (a) undisturbed laminar flow with purely diffusive mixing; and (b) perfectly mixed flow. Case (a) leads to a thin concentration boundary layer imbedded in the flow near the membrane surface. It is shown that for practically relevant parameters the solution may be approximated by a closed-form similarity solution, and this is compared with the more exact numerical solution. Case (b), which represents the ideal situation, is presented for comparison.