  Electro-sorption (ES) is a research frontier in electrochemical separation,
with proven potential applications in desalination, wastewater treatment, and
selective resource extraction. However, due to the limited adsorption capacity
of film electrodes, ES requires short circuiting or circuit reversal,
accompanied by solution-switch between the feed solution and receiving
solution, to sustain desalination over many charging-discharge cycles. In the
literature, solution-switch have been commonly ignored to simplify experimental
procedures and its impacts on separation performance are thus not well
understood. This study aims to provide a quantitative analysis of the impacts
of mixing due to solution-switch on the performance of ES-based desalination. A
numerical model of ES has been employed to evaluate the adverse effects of
solution-switch on the desalination performance in three different operation
modes. The analysis reveals that the impacts of mixing due to solution-switch
are more severe with a larger concentration difference between the desalinated
water and the brine and provides insights on the effectiveness of increasing
electrode loading or specific capacity in mitigating the detrimental impacts of
mixing. Even with state-of-the-art systems, producing freshwater from seawater
or even brackish water with medium-to-high salinity is practically challenging
due to the presence of solution-switch.
