Study of graphitic crystalline structure in highly porous activated carbons derived from rice husk biomass

Rice husk (RH) is a lignocellulosic material obtained from agricultural waste that can be converted into valuable carbon-rich materials through various thermochemical processes. However, its application is limited because some fundamental properties of RH biomass are still under investigation. This study focused on producing activated carbons (ACs) using alkaline chemical treatments, followed by a two-stage carbonization process in a nitrogen (N₂) gas atmosphere. Three distinct porous carbon materials were produced by varying the carbonization temperature and retention times. These materials are designated as AC-30 M, AC-60 M, and AC-90 M. All samples exhibited highly porous structures and outstanding surface properties. However, there were significant variations in pore geometry, surface area, and crystalline phases are largely dependent on the carbonization temperature and retention times. Ultimate analysis of the porous carbon materials revealed that the fixed carbon percentage increased from 51.2 to 58.4% with longer retention times. The Brunauer–Emmett–Teller (BET) surface area analysis was conducted to evaluate pore radius, pore volume, and active surface area. The results showed that AC-90 M exhibited the maximum pore volume of 0.374 cc/g and the highest surface area of 587.616 m²/g. The porous activated carbon materials were analyzed using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The results indicated the presence of both amorphous structures and graphitic crystalline phases within the well-developed porous structures, which was further confirmed by the International Center for Diffraction Data (ICDD) database.