A Hexagonal Honeycomb-Shaped Flow Channel for High-Efficient Desalination and Flowability in Flow-Electrode Capacitive Deionization

This work has a positive effect on the practical applicationof an FCDI device and technology in water desalination. Flow-electrode capacitive deionization (FCDI) is a prospectivealternative for large-scale desalination applications due to the efficientflowability of the electrode slurry. However, flow channel blockagesand slurry leakage in conventional FCDI cells have severely limitedthe salt removal and stable operation. Based on the synergistic effectsof diverting and guiding flow, a hexagonal honeycomb-shaped flow channel(HH-channel) was innovatively applied to the FCDI system to optimizethe hydrodynamic behavior of the slurry, which greatly reduced thehydraulic pressure and enhanced the desalination performance. Whatis more, we first introduced a Two-Phase Transport Mixture model andcombined it with computational fluid dynamics (CFD) simulations tofurther confirm that more uniform distribution of carbon particlesin the HH-channel facilitates the construction of a charge percolationnetwork and charge transfer compared to a serpentine single-trackflow channel (SS-channel) and rectangular-cavity flow channel (RC-channel).After a long-term operation test (1800 min, U = 1.6V), the FCDI system with the HH-channel exhibited superior desalinationstability, with a faster average salt removal rate (ASRR) of 2.05 & mu;mol cm(-2) min(-1) and saltremoval efficiency (SR) of 64.89% and charge efficiency (CE) of 96.06%.In summary, our work developed a facile strategy for optimizing theflow channel geometry to improve slurry flowability and obtain anefficient and steady desalination application.