Enhanced photocatalytic degradation of tetracycline using cobalt-doped CoxCdx−0.8Ba0.2Fe2O4 spinel ferrite nanoparticles: synthesis, characterization, and mechanistic insights
摘要
Pharmaceutical contamination in aquatic systems poses environmental challenges, with tetracycline antibiotics detected at 0.1–31.0 μg L−1 across 58 countries. This study reports the synthesis of cobalt-doped CoxCd0.8−xBa0.2Fe2O4 (X = 0, 0.4) spinel ferrite nanoparticles for the photocatalytic degradation of pharmaceutical pollutants. The nanoparticles were synthesized via a citric acid-assisted sol–gel method and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller, and ultraviolet–visible diffuse reflectance spectroscopy. Cobalt substitution reduced the crystallite size from 25.78 to 20.26 nm and narrowed the bandgap from 2.8 to 2.55 eV. The Co0.4Cd0.4Ba0.2Fe2O4 photocatalyst achieved complete tetracycline degradation (100%) within 75 min, compared to 53% degradation by undoped (Cd0.8Ba0.2Fe2O4) sample. Kinetic analysis revealed second-order degradation kinetics with a rate constant of k2 = 0.01173 L mg−1 min−1. The cobalt-doped catalyst exhibited a superior quantum yield (3.59 × 10−6 molecules photon⁻1) and space–time yield (2.40 × 10−7 molecules photon⁻1 mg−1), representing an 89% improvement over the pristine sample. Mechanistic studies have revealed that hydroxyl radicals (HO*) are the primary reactive species in this process. The addition of hydrogen peroxide accelerated complete degradation within 20 min via Fenton-like mechanisms. The catalyst exhibited stability, with an efficiency retention of over 93% over five cycles. These findings establish cobalt-doped ferrite nanoparticles as promising materials for water treatment.