Solar-Driven Degradation of Anionic Dyes Using Ultrasonically Synthesized Trimetallic Doped ZnO-Graphitic Carbon Nitride Nanocomposite Photocatalyst

We report an ultrasound-assisted green synthesis of 2% Bi2O3, Co3O4, and Fe2O3 co-doped ZnO/g-C₃N₄ nanocomposites. Structural and physicochemical analyses (XRD, FTIR, SEM/EDS, UV–Vis DRS, BET) confirm uniform dopant incorporation, enhanced light harvesting, and increased surface area. Under natural sunlight, the composite achieved 98.1% degradation of Indigo Carmine and 94.8% degradation of Xylidine Ponceau within 90 min, as shown by UV–Vis and TOC measurements. Optimization of pH, catalyst loading, and dye concentration, coupled with radical scavenging assays, identified •OH radicals as the primary reactive species. The catalyst retained over 78% of its initial activity after four successive cycles, demonstrating outstanding stability and reusability. This work introduces a sustainable, low-energy route and a novel trimetallic doping strategy for efficient remediation of organic pollutants.