Rapid Synthesis of Graphitic Carbon Nitride Nanosheets for Adsorption of Cationic Dyes

Abstract Toxic dyes in wastewater threaten aquatic ecosystems, underscoring the need for sustainable treatment methods. This study presents a rapid synthesis of graphitic carbon nitride nanosheets (g-C₃N₄ NS), annealed in air at 550°C for 2 hours via thermal polymerization of thiourea. These nanosheets serve as adsorbents for removing cationic dyes such as methyl blue (MB) and rhodamine B (RhB). The structural and morphological properties of the synthesized g-C₃N₄ NS were examined using various analytical techniques. XRD confirmed the presence of a hexagonal phase, while FT-IR identified nitrogen-rich heterocyclic structures. SEM and TEM imaging illustrated the successful formation of g-C₃N₄ nanosheets with edge thicknesses ranging from 6.9 to 20.88 nm. BET analysis revealed a Type IV structure, characterized by a surface area of 101.2 m²/g and an average pore size of 7.01 nm. Adsorption experiments with 20 mg of g-C₃N₄ NS at a concentration of 25 mg/L and pH 7.5 demonstrated that RhB is adsorbed more efficiently than MB. Analysis indicated that adsorption follows the Freundlich isotherm and pseudo-second-order kinetics, suggesting a spontaneous, endothermic process that enhances disorder at the solid/solution interface. Reusability tests showed that g-C₃N₄ retained over 85% efficiency after five cycles, confirming its potential as a sustainable and cost-effective solution for dye removal.