Fast photocatalytic oxidation of ciprofloxacin over Co3O4@CeO2 heterojunctions under visible-light

• Synthesis of Co 3 O 4 @CeO 2 by surfactant-based sol–gel/ calcination technique. • Co 3 O 4 addition can effectively improve the physicochemical, optical, and photocatalytic properties. • Complete ciprofloxacin photodegradation achieved in 30 min over Co 3 O 4 @CeO 2 . • The degradation rate of 15% Co 3 O 4 @CeO 2 was 2 times higher than pristine CeO 2 . • Co 3 O 4 @CeO 2 can be recycled five times without loss in its activity. : The widespread dispersal of antibiotic waste in freshwater has accelerated the water contamination that impacts the ecosystem. Moreover, different studies have discussed the expected green mineralization of such contaminants. : Herein, a unique Co 3 O 4 @CeO 2 nanocomposite was developed by incorporating different doses (5–20 wt%) of Co 3 O 4 nanoparticles (NPs) using a surfactant-based sol–gel/ calcination technique. The photocatalytic activity of Co 3 O 4 @CeO 2 nanocomposites was estimated in the degradation of ciprofloxacin (CIP) antibiotic under visible exposure. : Optimizing the Co 3 O 4 mass yields a bandgap semiconductor of 2.66 eV with a wide visible light. The 15% Co 3 O 4 @CeO 2 nanocomposite displayed the best CIP destruction performance after 45 min, with 2-fold greater activity than pure CeO 2 NPs. After 30 min of visible light illumination, 2.4 gL −1 dosage of 15% Co 3 O 4 @CeO 2 achieved complete CIP oxidation with a photoreaction rate of 0.12 min −1 and retained significant reusability after five runs. The explanation for the improved photocatalytic efficiency of the Co 3 O 4 @CeO 2 is postulated based on the effective segregation of photoinduced charge carriers via an S-scheme mechanism, where electron–hole pairs can easily move between CeO 2 and Co 3 O 4 because of their matched band locations. This research corroborates the use of nanoheterojunction oxides in rapidly removing antibiotic residues under visible light.