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Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In the salt removal step, ions are adsorbed at the carbon–water interface within the micropores inside the porous electrodes. After the electrodes reach a certain adsorption capacity, the cell voltage is reduced or even reversed, which leads to ion release from the electrodes and a concentrated salt solution in the spacer channel, which is flushed out, after which the cycle can start over again. Ion-exchange membranes are positioned in front of each porous electrode, which has the advantage of preventing the co-ions from leaving the electrode region during ion adsorption, while also allowing for ion desorption at reversed voltage. Both effects significantly increase the salt removal …