Unraveling the Photocatalytic Performance of La₂O₃ Nanoparticles for the Degradation of Six Organic Dyes

Lanthanum oxide (La₂O₃) nanoparticles stand out as promising photocatalysts due to their remarkable stability and photocatalytic properties. In this study, La₂O₃ nanoparticles were synthesized via a hydrothermal method and explored how varying calcination time (3 and 5 h) influences their structural, morphological, optical, and catalytic properties. X-ray diffraction (XRD) confirmed stable hexagonal structure, with crystallite sizes increasing from 32.79 to 45.49 nm, while UV-vis absorption studies revealed that increasing calcination time led to a gradual decrease in bandgap energy from 4.6 to 4.4 eV, making the material more effective at utilizing light for pollutant degradation. When tested against a range of organic dyes, La₂O₃ nanoparticles calcinated for 5 h exhibited the highest degradation efficiencies, due to their improved crystallinity and enhanced charge carrier movement. The photocatalytic process followed first-order kinetics, and recyclability tests showed that the nanoparticles retained their efficiency over multiple cycles. Radical scavenger tests confirmed that hydroxyl radicals (^•OH) and superoxide radicals (^•O₂^-) were the dominant reactive species involved in dye degradation, affirming the key mechanism behind the observed photocatalytic performance. These results highlight how fine-tuning calcination time can significantly enhance La₂O₃'s potential, making it an eco-friendly solution for wastewater treatment.