Hybrid Electrochemical Desalination System Combined with an Oxidation Process

Here, we report a novel hybrid electrochemical desalination system synchronized with an oxidation process for the first time. As one of the breakthroughs in electrochemical desalination systems, the oxidation process is demonstrated as a strategy to overcome the drawbacks of electrochemical desalination systems associated with the difficulties of anion adsorption/intercalation. This hybrid system consists of a cation-selective battery material in the desalination component, an oxidant generating anode in the oxidation component, and an anion exchange membrane that offers a channel for the diffusion of anions. During the operation, cations are intercalated into the battery material, and reactions occur on the anode to generate reactive chlorine species (e.g., Cl₂, HOCl, and ^•Cl), and reactive oxygen species (e.g., H₂O₂, ^•OH, and O₃). Simultaneously, the anions in the desalination component diffuse into the oxidation component to maintain the neutrality in each component. By utilizing the diffusion of anions through an anion exchange membrane, the desalination process can be performed with only the cation-selective battery material, leading to enhancement of the desalination capacity, and generated oxidants on the anode can be utilized in electrochemical water treatment process. As a primary result, a specific capacity of approximately 33 mAh g^-1 was successfully utilized as the desalination capacity with a Coulombic efficiency of over 96% in 7.2 g L^-1 of NaCl, indicating 28 mg of Na was desalted per gram of cation-selective battery material and 44 mg of Cl diffused. Through the combination of an oxidation process with a desalination system using energy storage materials, the research and application of the electrochemical water treatment system are expected to be expanded.