Fig. 5.

Schematic overview of a CDI cell for the removal of pH-dependent ions. (A) The FTE CDI cell consists of two porous electrodes with a porous layer (“separator”) in between. Feedwater, which contains inert and pH-dependent ions, flows through the separator and ions are electrosorbed by the electrodes. (B) In the macropores, which serve as transport pathways, the local pH is evaluated at each position, as well as the pH-dependent chemical equilibria between ions and H⁺ and ${\mathrm{O}\mathrm{H}}^{-}$. (C and D) Ions are electrosorbed in the micropores which have chemical surface groups with pH-dependent charge. Acidic (C) and basic (D) regions.