The research progress on the removal of heavy metals using carbon electrodes in capacitive deionization technology

Abstract The challenge of freshwater pollution emerges as a paramount concern in the 21st century, necessitating innovative solutions for sustainable water management. Among various technologies, Capacitive Deionization (CDI) stands out as an electrochemical method with significant promise due to its environmentally benign nature, cost efficiency, minimal energy requirements, and the simplicity of electrode regeneration. The technology leverages a variety of carbon-based materials such as carbon nanotubes, MOF-derived carbon, bio-derived carbon, activated carbon fibers, and graphene oxide as electrodes. These materials are selected for their superior electrical conductivity, structural flexibility, and large surface areas, which are crucial for the efficient removal of heavy metals from polluted water sources. Nonetheless, the reliance of carbon electrodes on the electrical double-layers adsorption mechanism may limit their adsorption capacity and selectivity towards specific contaminants. This review paper delves into the current challenges, optimization strategies, and recent progress in enhancing the efficacy of carbon materials for heavy metal ion extraction in CDI processes. It further discusses the prospective developments in carbon materials and their derivatives for the improvement of heavy metal removal capabilities, providing insightful perspectives on the advancement of CDI technology as a pivotal approach to addressing the issue of freshwater pollution.