Enhanced photodegradation of ciprofloxacin by Cu-doped spinel ferrite nanoparticles: synthesis, characterization and mechanistic insights

This study introduces CuxSr1-xAl0.4Fe1.6O4 (X = 0, 0.4) as a novel photocatalyst synthesized via the sol-gel method for ciprofloxacin degradation in water systems. This composition, which combines strontium, aluminum, and copper in a spinel ferrite structure, represents a significant advancement in antibiotic remediation technology. Key findings reveal that copper doping decreased the bandgap from 2.8 to 2.6 eV, increased surface area by 38% (from 31 to 43 m2/g), and dramatically enhanced photocatalytic performance. The Cu-doped catalyst achieved 100% ciprofloxacin degradation within 75 min under optimized conditions of pH 7, 30 °C, 10 mg catalyst dosage, and 10 ppm ciprofloxacin concentration, with a second-order rate constant of 0.00756 L mg−1 min−1 under visible light irradiation (100 mW/cm2)., compared to only 54% for the undoped material. Hydroxyl radicals were identified as the primary reactive species, with degradation following second-order kinetics. The catalyst maintained over 94% efficiency after recycling five times, demonstrating its excellent stability. With superior quantum yield (3.21 × 10⁻⁶ molecules/photon) and minimal catalyst dosage requirements, this material offers a sustainable solution for the remediation of pharmaceutical contaminants. The findings have significant potential for implementation in pharmaceutical wastewater treatment plants and water purification systems.