Design principles for enhanced up-scaling of flow-through capacitive deionization for water desalination

To develop efficient and cost-effective desalination technologies is crucial for addressing the globally increasing needs for drinking water. One such desalination technology that is growing is capacitive deionization (CDI), wherein ions are electrically removed from water passing through or between two porous conducting electrodes. As the CDI field grows, design principles for scaling from small CDI cells to larger units and modules will become increasingly important. Thus, we have investigated the flow distribution in single flow-through CDI cells and interconnected modules to determine architectural principles that can feasibly reduce the pressure drop with good throughput, thus increasing energy efficiency. The most important principles found include massive parallelism, open regions to symmetrically distribute flow, and tailoring the permeability of the electrodes and spacers. Crucially, we demonstrate how simply rerouting the flow reduces the pressure drop through the cell by a factor of four in a two-cell system. Finally, we leverage the found principles to a cylindrical CDI cell well-adapted to modular up-scaling. In conclusion, implementing the design principles leads to a significant reduction in pressure drop and energy consumption of a CDI system, which is essential for upscaling to larger modular systems for practical use.