Continuous capacitive deionization with regenerative rotating film electrodes

Abstract

In the present study a new continuous capacitive deionization system is presented with intermediate bipolar rotating film-electrodes. Due to the applied electric field and the effect of electrostatic shielding, the bipolar electrodes are polarized and adsorb electrostatically counterions at their outer sides. Simultaneously, due to contact and short-circuiting in the middle, the oppositely charged electrode sides are discharged and release the adsorbed counterions. Charging and discharging occur at the same time without any need for rearrangement or electrical connection/disconnection to/from the power source. The cycle is boundlessly repeated and the deionization process continuous. The consumed electrical energy needed for polarization of the electrodes is to a high extent recovered by the simultaneous depolarization. With the new proposed continuous capacitive deionization system, brackish water of various initial concentrations 1–3 g/L NaCl, is separated in a desalinated and a concentrated water stream. The electrical energy consumption is over 60% lower than reported with the prior art capacitive deionization devices. Water recovery 80:20 and simultaneous continuous regeneration of the electrodes are achieved by applying current densities 4.45 to 32.6 A/m2 and flow rates 1.5 to 7.5 mL/min.