Numerical Modeling of a Desalination Process Through the Ion-Exchange Membranes of a Electrodialysis Cell

A bi-dimensional electrodialysis unit cell model was developed in this study by using a Finite Element Method (FEM) technique. This model, implemented with Comsol Multiphysics software, considers a variable current density along the flow direction at a constant voltage drop due to a variation in salt concentration. Ion and charge transport, current density and potential profile along the cell were numerically investigated here. Nernst-Planck equation with three modes of mass transport (diffusion, migration, convection) and Navier-Stokes equation, completed with Faraday's law and Nernst- Einstein equation were involved in the design. The cell model was based on interpolymer type ion exchange membranes of 0.13 and 0.18 mm thickness, with specific ionic conductivities at NaCl feed concentrations of 0.1 M and 0.25 M. Limiting current density (LCD) for the two - unit cell models was evaluated at different linear feed velocities using Lee - Strathmann model.