Efficiency of capacitive deionization using carbon materials based electrodes for water desalination

Capacitive deionization (CDI) based on electrosorption has been considered an important methodology for desalination process due to its lower energy consumption, easier electrode maintenance and regeneration, when compared with conventional desalination techniques based on membrane separation or thermal distillation. New electrodes for CDI desalination have been prepared in the last years with several types of carbon nanomaterials and inorganic nanoparticles, resulting in a large number of articles and patents. Thus, an impressive number of works have recently arisen, and new revisions with different point of views appeared. In this short review, it is shown the last advances and contributions in electrodes for CDI, obtained by different types and combinations of carbon materials, and their efficiency in the desalination process. The new approach of this work is the comparison of the removal efficiency for different salts (not only NaCl), both at articles and patents, to produce a quantitative comparison of the electrode materials used in this field. The removal efficiency was classified in three levels for the case of NaCl electrosorption (high, moderate and low) and specified also for salts containing Fe3+, Mn2+, Cr3+, Cd2+, NO3−, SO42− for instance. Therefore, this work can be useful as guideline of materials for electrodes for specific applications into this relevant technological and scientific field and its challenges in relation to the increasing demand by fresh water in the world.