Recent progress on the application of capacitive deionization for wastewater treatment

Capacitive deionization (CDI) is an emerging technology for removing charged ions from wastewater or aqueous solutions, where the charged ions interact electrostatically with the porous electrodes. Although recently, studies on CDI have increased significantly, the bulk of them is related to desalination (removing NaCl from water). So, it is highly recommended to highlight and discuss the CDI's capability to treat wastewater. This review summarizes the principles and application of CDI technology in wastewater treatment. The significant developments made on CDI for removing water containments such as radioactive minerals, heavy metals, nutrients, halides, hardness, and acids are highlighted. Then, CDI integrated or hybrid systems, such as co-precipitation, ultrafiltration, reverse electro-dialysis, electro deionization, and adsorption, for wastewater treatment and ion removal are reviewed and discussed. Finally, recommendations and future aspects for CDI development are presented.