Capacitive deionization for simultaneous removal of salt and uncharged organic contaminants from water

Abstract

Capacitive deionization (CDI) has been solely employed for the removal of charged ions from water, showing limited feasibility compared to other conventional technologies such as reverse osmosis (RO). In this work, we propose to use CDI with activated carbon electrodes for simultaneous removal of inorganic salt and trace organic contaminants (TOrCs). This approach is based on the inherent sorption potential of activated carbon CDI electrodes towards organic species. We show that salt removal by CDI is only slightly affected by the presence of different TOrCs (bisphenol A, carbamazepine, estrone, and phentoxifylline). Sorption and removal of TOrCs (taking place concomitantly) was most effective for the hydrophobic compounds (bisphenol A and estrone) and was not affected by the presence of salt or the applied electric field. Sequential desorption of salt and TOrCs into two separated streams was achieved by short-circuiting the two electrodes and washing the electrodes with water and ethanol, respectively. Notably, the described process produces separate waste streams for salts (i.e., water) and organics (i.e, ethanol), which can facilitate their disposal or further treatment. Altogether, the study shows the high potential of the proposed CDI application, which may be valuable for treating water or wastewater streams contaminated with both salt and TOrCs.