Potential and concentration gradients in a hybrid ion-exchange/electrodialysis cell

The regeneration of 2, 4 and 8% cross-linked ion-exchange resins in the nickel-form was carried out in a three-compartment hybrid ion-exchange/electrodialysis cell. During the process the potential and nickel concentration profiles in the bed were measured. The experimental results are compared to results from a one-dimensional transport model able to simulate the development of potential and concentration gradients during the process; the amount of nickel transported out of the ion-exchange bed to the cathode, or concentrate, compartment was also reasonably well predicted. Differences between the model and experimental results are also discussed. It was found that under extreme conditions (i.e., high bed voltage), the formation of metallic nickel was observed in the central ion-exchange compartment.