A new method to determine the optimal operating current (Ilimʹ) in the electrodialysis process Original Research Article

According to classical electrodialysis (ED) theory, measuring limiting current (Ilim) with an assembled stack is a commonly used technique to decide operating current. The current/voltage method of recognizing limiting current does not always yield unambiguous estimates of the limiting condition when applied to a practical electrodialysis apparatus. Some researchers have suggested an arbitrary method of using current/voltage data. Considering that the aim of ED was to obtain high desalting efficiency, a new parameter regarding the optimal operating current has been defined as Ilimʹ, and a new method to determine Ilimʹ was proposed to guide the operation of the ED process in this paper. This method consisted of measuring current as a function of desalting efficiency and determining the inflexion in a η-I curve. To prove the feasibility of Ilimʹ, the V–I, V/I–I and η-I curves were plotted and compared by using NaCl aqueous solutions at different conductivities. The experimental results showed that Ilimʹ determined by the η-I curve was exactly located between the two inflexions in the V–I and V/I–I curves. A method of combining the η-I curve with the V/I–I curve was proposed to decide the range of operating current. Compared to the current/voltage method, this method is more readable and practical.