Capacitive Deionization Coupled With Electrochemical Oxidation for Chemical Oxygen Demand Removal

ABSTRACT

The treatment of industrial wastewater containing refractory organics contributing to chemical oxygen demand (COD) remains a critical environmental challenge. Here, an integrated electrochemical oxidation‐capacitive deionization (EO‐CDI) system based on an ionization‐electrosorption mechanism is developed. In this design, the EO unit serves as a low‐energy conversion stage rather than a complete mineralization process, transforming refractory organics into ionizable intermediates that are subsequently removed by electrosorption in the CDI unit. Chromatographic analyses confirm the formation of carboxylic acid intermediates and their subsequent removal, validating the proposed ionization‐electrosorption pathway. For simulated phenol wastewater, the system achieves 80% COD removal. For chloride‐containing industrial wastewater with a complex ionic composition (∼200 mg L ⁻¹ COD, ∼10 mS cm ⁻¹ ), stable COD removal of 95% is achieved with a low specific energy consumption of 7.6 kWh m ⁻³ . Moreover, the EO‐CDI system maintains stable performance over 50 operating cycles. These results demonstrate that the EO‐CDI hybrid system provides an energy‐efficient and robust strategy for advanced industrial wastewater treatment.