Exploring the potential of Ti3+ in TiO2 through experimental analysis and response surface methodology: Photocatalytic degradation of pharmaceuticals

Unregulated release of pharmaceuticals (PhACs) persists in the environment due to their non-biodegradable and highly stable nature. In this study, Ti 3+ induced TiO 2 nanoparticles (NPs) (7.5 nm average crystallite size) were synthesized through a facile hydrothermal process. Powder X-ray diffraction revealed anatase phase of TiO 2 NPs with a band gap of 3.48 eV. The observed bands in Raman spectroscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy confirmed the oxygen vacancies and formation of Ti 3+ in TiO 2 lattice structure. The nanoparticles exhibited proficient photocatalytic degradation of 97% paracetamol (PCM) in 120 min, 95% diclofenac (DCF) in 30 min, and 72% chloramphenicol (CRP) in 120 min. The PCM degradation pathway was analyzed via mass spectroscopy, revealing key steps like coupling, hydroxylation, oxidation, and deacylation. Crucial process parameters (catalyst dose, initial PhAC concentration, pH, and time) were optimized for PCM, DCF, and CRP photocatalytic degradation, with kinetics following the Langmuir–Hinshelwood pseudo-first-order model. Response Surface Methodology-Central Composite Design optimized independent variables, showing higher DCF degradation efficiency at high catalyst doses and an optimal pH of 5.5–7. The role of radical species in the photocatalytic degradation of PhACs was discussed using EDTA-Na 2 , terephthalic acid, and p-BQ for holes, OH • , and O 2 −• radicals, respectively.