Impact of cation-exchange membrane scaling nature on the electrochemical characteristics of membrane system

The membrane fouling formation during electrodialysis of complex solutions is one of the main issues affecting the process performance and costs. This work was focused on the investigation of electrochemical behavior of membrane systems containing a cation-exchange membrane whose surface was affected by mineral fouling of different composition. Together with the scaled membranes, the pristine membrane was studied for comparison. For membrane without scaling on its surface, it was found that the limiting current value exceeded the one theoretically calculated by the convection-diffusion model. It is most likely related to equilibrium electroconvection developed at the membrane surface. The presence of magnesium and calcium hydroxides on the membrane surface leads to an intensification of water splitting at the depleted membrane surface, resulting in suppression of electroconvection and reduction of the overlimiting current. The presence of calcium carbonate on top of magnesium and calcium hydroxides prevents their contact with water molecules. The current-voltage characteristic of such membrane system was almost identical to the characteristics of the membrane system containing the pristine membrane. To our knowledge, it was the first time that the impact of scaling nature on the electrochemical behavior of membrane system was revealed and the relative mechanismi identified and explained.