Development of biochar electrode materials for capacitive deionization: preparation, performance, regeneration and other challenges

Capacitive deionization (CDI) is a potential cost-efficient desalination technology. Its performance is intrinsically limited by the structure and properties of the electrode materials. Biomass materials have become a research hotspot for CDI electrode materials because of their abundance, low cost, and unique structure. The preparation, desalination performance, and regeneration status of biochar electrodes are summarized and clarified. Their preparation and use in CDI in recent years are presented and compared, and the effects of biochar electrode materials and CDI operating parameters on the desalination performance are emphasized. It is found that the salt adsorption capacity is positively correlated with the percent mesoporous material they contain. The selective adsorption of ions mainly depends on ion properties like ionic radius and charge as well as voltage, charging time and feed water characteristics. The current status and methods of electrode regeneration are discussed and future developments are suggested.