Visible-light-driven photocatalysis using g-C₃N₄ based ternary composite: a synergistic approach for effective degradation of organic pollutant

The widespread pollution of water resources by synthetic dyes and aromatic compounds has become a critical environmental challenge. To address this, we developed a novel photocatalyst, g-C₃N₄-modified ZnO/La₂O₃ nanocomposite, engineered for effective degradation of methylene blue (MB) dye and benzoic acid under visible light irradiation. The material’s physical and optical properties were evaluated through XRD and UV–Visible spectroscopy, revealing its crystalline integrity and strong light absorption behavior. Under visible light illumination, the composite achieved promising degradation rates of over 90% for methylene blue and 68% for benzoic acid within 120 minutes. Compared to the binary ZnO/La₂O₃ system, the g-C₃N₄ enhancement significantly improved charge separation and broadened the absorption spectrum, resulting in faster reaction kinetics. The calculated rate constants were 0.01813 min⁻¹ for MB and 0.0213 min⁻¹ for BA. The photocatalyst maintained its performance across multiple reuse cycles, demonstrating excellent stability. Mechanistic studies identified electrons, holes, and hydroxyl radicals as key reactive species in the photodegradation reaction. Additional tests, including pH variation and measurement of total organic carbon (TOC), verified the material’s adaptability and mineralization capability. These findings position g-C₃N₄@ZnO/La₂O₃ as sustainable solution for wastewater treatment technologies.