Enhancing desalination efficiency via structurally optimized symmetrical flow channels in flow-electrode capacitive deionization (FCDI)

Flow-electrode capacitive deionization (FCDI) is a promising desalination technology recognized for its high salt removal capacity. However, conventional FCDI systems face structural limitations under elevated flow conditions, where phenomena such as hydraulic short-circuiting and leakage significantly compromise performance and operational stability. To overcome these limitations, this study introduces an advanced FCDI system featuring a mirror-symmetric serpentine design in both the flow channel and gasket. This precisely symmetrical and tightly compressed structure provides internal rigid support, specifically designed to minimize membrane module and flow channel deformation while withstanding high hydraulic pressures and ensuring operational stability. At an optimal flow rate of 200 mL min −1 (SCC mode, 1.2 V), the system achieved a charge efficiency (CE) of 127.92 % and an average salt removal rate (ASRR) of 3.24 μmol cm −2 min −1 . Coupled computational fluid dynamics (CFD) simulations of the flow and electric fields, combined with adsorption process analysis, identified flow-enhanced ion transport at the membrane interface as a key factor contributing to the high charge efficiency. Further optimization yielded an ASRR of 6.14 μmol cm −2 min −1 and a CE of 115.48 % at 2.0 V, demonstrating superior desalination rates and energy efficiency. Long-term stability tests validated the system’s durability and leakage-free performance under sustained operation. These findings highlight the feasibility and scalability of this optimized FCDI system as a high-performance solution for large-scale desalination applications.