Impact of flow configuration on electrosorption performance and energy consumption of CDI systems

The flow configuration selected for a capacitive deionization (CDI) system can impact the desalination performance due to drastic changes to the ion transport. Herein, a zero-gap CDI cell fixture with various flow configurations was utilized to investigate the effects of flow directionality on the CDI performance of activated carbon cloth (ACC) electrodes. Salt adsorption capacities and salt adsorption rates were determined for three commonly studied flow field designs (parallel (PFF), interdigitated (IDFF), and serpentine (SFF)) at various flow rates (2–128 mL/min). Increasing the flow rate was found to result in decreasing CDI performance for SFF and IDFF designs. On the other hand, the peak performance was observed for the parallel flow field at 32 mL/min flow rate. Additionally, the pressure drop values for different flow configurations were measured, and the energy consumptions were calculated. Overall, the findings showed that the performance of CDI systems strongly depends on the selected flow field geometry. Among the tested flow fields, the parallel configuration offered the best balance between CDI performance and energy efficiency. However, the designs that exert high hydrodynamic forces on the electrode plane showed poor performance due to rip-off of ions from the double layer causing a significant capacity loss for ACC electrodes.