A further process for the separation of ions from an aqueous solution is capacitive deionization. Here the ions to be separated move according to their charge to the anode or cathode and charge these like a plate capacitor. Unlike other processes such as electrodialysis, however, no charge transfer takes place among the ions or with the electrodes, which is why this technology requires only low voltages of around 1.6 V. The energy consumption is therefore low. Once the charging capacity of the electrode is reached (if a capacitor is completely charged), the concentrate is released by polarity reversal and discharged as a concentrated electrolyte.
Together with our project partners in the EU project “REWAGEN” – after the separation of oils and particulate contaminations as well as the degradation of the organic load – we also finally remove dissolved salts in a fourth stage using capacitive deionization. The process is outstanding when combined with electrodialysis, as this makes available a concentrate, which additionally increases its efficiency significantly.