A Novel Method for Limiting Current Calculation in Electrodialysis Modules

Abstract

The purpose of this work was to develop a novel semi-empirical method for calculation of limiting currents in electrodialysis modules. Experiments were carried out at pilot-scale module with five electrolytes. Current-voltage curves were measured and limiting currents were determined. Subsequently, dependence of the mass transfer coefficient on linear flow velocity was evaluated and its parameters a, b were estimated. The main advance of this work is that comparison of electrolytes showed the clear relationship between parameter a, electrolyte diffusion coefficient and the difference of cation transport numbers in membrane and solution. The semi-empirical relationship between the mass transfer coefficient and linear flow velocity was set up, and the limiting current calculation run was proposed. At the same time, dependence of the diffusion layer thickness on linear flow velocity was examined and the way of its calculation was established. The proposed method is unique thanks to its applicability in a broad range of experimental conditions; its use is not limited neither by electrolyte type nor electrodialysis module size.