Integrating electrochemical oxidation and flow-electrode capacitive deionization for enhanced organic degradation and perchlorate removal in high salinity waters

This study aimed to assess the application of an electrochemical oxidation (ECO) and flow-electrode capacitive deionization (FCDI) sequential hybrid process for the treatment of high-concentration ions, organic pollutants (i.e., humic acid, alginate, benzoic acid, phenol, and 4-chlorophenol), and marine algae. The ECO system led to the rapid generation of reactive chlorine species (RCS) via anodic oxidation of the boron-doped diamond (BDD) electrode under optimum current in the NaCl-based feed solution, which caused the reduction of total organic carbon (TOC) and the degradation of algae cells. However, the formation of undesirable by-products (i.e., toxic perchlorate) was triggered by direct electrolysis. Concurrently, the optimal operational conditions of the FCDI system were evaluated based on the monitoring of process performance according to various parameters (i.e., applied voltage, electrode mass loading, electrolyte concentration in the flow electrode, feed solution concentration, and adsorption/desorption phase operation). Finally, the superiority of the ECO–FCDI hybrid process was confirmed and clearly demonstrated via the effective decomposition of organic compounds and the complete removal of toxic perchlorate by-product together with the effect of deionization. To the best of our knowledge, this work is the first to develop and apply the ECO–FCDI integrated process for the removal of a broad spectrum of pollutants (including both organics and ions) and to attain successful desalination.