Enhanced capacitive deionization desalination provided by chemical activation of sugar cane bagasse fly ash electrodes

Sugar Cane Bagasse Fly Ash (SCBFA) is an abundant low-cost high content carbon bio-waste material. In this manuscript, different chemical activation agents, such as ZnCl₂ and KOH, have been explored as a mean of improving physical and electrochemical properties of SCBFA as an electrode material for capacitive deionization (CDI). The study determined that the activation with high mass ratios of ZnCl₂ led to a low electrosorption of salt and high charge density. These results seemed to be a consequence of the residual Zn that led to parasitic reactions reducing charge efficiency. An intensive cleaning procedure resulted in a higher electrosorption due to a reduction of Zn contain although complete Zn removal was not achieved and this might pose eventual environmental issues. KOH activation had a significant positive impact on enlarging the specific surface area and increasing the number of polar surface oxygen groups (SOG). These modifications led to a large increase in specific capacitance (from 12 to 72–86 F g⁻¹) and salt adsorption capacity (48–74%). Moreover, SOG increment reduced the SCBFA hydrophobicity improving ion transport and leading to faster electrosorption kinetics. These findings support the potential of chemically activated SCBFA as a CDI electrode material for brackish water desalination.