Ultrasonically assisted synthesis of g-C3N4-activated carbon composite for enhanced defluoridation of water

Abstract

Fluoride contamination in drinking water poses a health threat. Activated carbon suffers from low fluoride adsorption capacity, which can be enhanced by loading with nitrogen-rich compounds. In this study, graphitic carbon nitride (g-C3N4) nanosheets were loaded onto activated carbon using ultrasonic irradiation to synthesize a g-C3N4-activated carbon composite. The ultrasonically synthesized composite exhibited significantly higher fluoride removal capacity of 92.7 mg/g compared to 2.1 mg/g for activated carbon alone. The adsorption followed the Langmuir isotherm model. Thermodynamic analysis revealed the adsorption was spontaneous and exothermic. Characterization confirmed the role of surface complexation between fluoride ions and C-N/CN groups in g-C3N4 for the enhanced adsorption. The composite achieved 82–90% defluoridation of real wastewater samples containing initially 8.7–12 mg/L fluoride. The composite could be regenerated using NaOH and reused for multiple cycles. The study demonstrates the potential of a simple ultrasonic irradiation method for synthesizing a g-C3N4-activated carbon composite with remarkably enhanced defluoridation capacity. The composite is promising for practical decentralized water defluoridation applications, especially in regions affected by high fluoride levels.