Recent advances in the fixed-electrode capacitive deionization (CDI): Innovations in electrode materials and applications

Conventional capacitive deionization (CDI), originally developed as a promising desalination technique based on the formation of electric double layers (EDLs) at the surface of porous electrodes, has recently shown significant advancements. Notably, the utilization of pseudocapacitive electrodes has demonstrated the capability to enhance salt adsorption capacity (SAC) and selectivity of specific ions. This comprehensive review encapsulates the latest research endeavored in CDI, with an emphasis on electrode materials and their role in augmenting SAC. The development of electrode materials has broadened the scope of CDI applications on the water and wastewater treatment and resource recovery. Hence, we also evaluated the manifold applications of CDI, including resource recovery (e.g., lithium, phosphate and nitrate), anion removal (e.g., fluoride, sulfate, chromium and arsenic), water softening, and the removal of heavy metals (e.g., nickel, cesium, lead, copper, cadmium and chromium) in addition to the water desalination. Lastly, we provide a forward-looking perspective on forthcoming research directions and potential developments within the realm of CDI technology.