Valorizing Biomass Reuse by Synthesis of Graphitized Carbon for Capacitive Deionization of Brackish Water: Experimental and Kinetic Study

Abstract This study explores a sustainable approach to desalinating brackish water using capacitive deionization (CDI). Biomass derived from agricultural wastes, like rice husk (RH), rice straw (RS), and bagasse ash (BG) are used to prepare graphitized carbon (GC). In this study, a novel approach to preparing GC has been followed. The GC was prepared through a two‐step graphitization and activation process using KOH or H 3 PO 4 . KOH activation at higher temperatures results in increased specific surface area, leading to an increase in the specific capacitance. The highest specific capacitance of 477 F/g was observed for the RH samples heated at 900 °C due to its high SSA of 535 m 2 /g. The study also investigates the ex situ kinetic and performance of the three electrodes, revealing a discrepancy between the external and internal diffusion behavior of ions. The same trend is observed in their performance as a supercapacitor. The salt removal capacity for the RH900K sample reached 10.29 mg/g at 612 mg/L at comparatively lower power consumption. The results indicated the enhancement in the CDI performance achieved by the two‐step activation process for the three samples studied compared to previous results, implying the potential of using such a process in the production of CDI electrodes.