Application of Capacitive Deionization in Water Treatment and Energy Recovery: A Review

Water resources are the basis for human survival and development. However, human beings face severe challenges of water pollution and freshwater shortage. With the critical advantages of low energy consumption, high efficiency, low cost, green and pollution-free, and renewable electrodes, capacitive deionization (CDI) has become an up-and-coming water treatment technology. After decades of development, the application of CDI has expanded from seawater desalination to many fields. However, the existing literature still needs a comprehensive overview of the multi-functional application of CDI technology in water treatment. Therefore, our work critically reviewed the latest research progress of CDI in water treatment to meet the technical requirements of various application fields. This paper first summarizes the various applications of CDI in water treatment, focusing on CDI's representative research results in heavy metal removal, organic contaminants removal, water softening, phosphate and nitrate removal, and water disinfection. In addition, we also discussed the latest research progress of energy recovery and energy consumption assessment for the CDI process. Finally, this paper discusses the challenges and future opportunities facing CDI technology.