The influence of flow electrode channel design on flow capacitive deionization performance: Experimental and CFD modelling insights

Flow capacitive deionization (FCDI) is an emerging desalination technology at which flow electrodes (shearthinningflowable carbon slurries) are used to remove ions from saline water. The geometry of flow electrodechannels, which provide the path and ensure the distribution and mixing of the flow electrodes, is one of the mostimportant aspects to be optimized. This work presents experimental and computational fluid dynamics (CFD)modelling analysis of the influence of the geometry of flow electrode channels on FCDI performance. Flowelectrode gaskets (with open, serpentine (short) horizontal and serpentine (long) vertical channels) were 3Dprinted using a polyethylene terephthalate glycol (PET-G) filament. The FCDI cell with a vertical serpentine flowelectrode channel exhibited the poorest performance due to channel blockage by carbon particles, while the bestresults were achieved with a horizontal serpentine flow electrode channel. CFD simulations aided in understandingthis behaviour by showing that the channel geometry strongly affects the local shear rate, and thus thelocal viscosity of flow electrodes. Thus, it is recommended to design channels that induce flow disturbanceaiming for increasing the shear rate and hence reducing flow electrode viscosity, therefore promoting theirflowability and reducing clogging chances.