Sunlight-Activated Photocatalysis of Organic Dyes Using TiO₂ Nanoparticles Prepared by Co-Precipitation

TiO₂ nanoparticles were successfully synthesized via a simple co-precipitation method at pH 11, 70°C for 2 hours, followed by calcination at 500°C for 2 hours. The crystalline structure and phase purity were confirmed by X-ray diffraction (XRD) and Raman spectroscopy, revealing a pure anatase phase. High-resolution transmission electron microscopy (HRTEM) showed well-dispersed spherical nanoparticles with an average size of 25.44 nm (SD = 6.7 nm). The photocatalytic activity of the synthesized TiO₂ nanoparticles was evaluated for the degradation of Methylene Blue (MB), Rhodamine B (RhB), and Crystal Violet (CV) dyes under direct sunlight. High degradation efficiencies were observed: ~99% for MB in 100 minutes (k = 0.05147 min⁻¹), ~ 98% for RhB in 140 minutes (k = 0.02743 min⁻¹), and ~ 98% for CV in 160 minutes (k = 0.02409 min⁻¹), despite the relatively large band gap of TiO₂ (3.2 eV). The differences in degradation rates are attributed to the molecular structures of the dyes and their susceptibility to reactive oxygen species generated by photoexcited TiO₂, with MB degrading the fastest and CV degrading the slowest. These results demonstrate the excellent potential of TiO₂ nanoparticles for sustainable, sunlight-driven degradation of organic dyes, highlighting their practical application in wastewater treatment and environmental remediation.