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

•Synthesis of Co3O4@CeO2 by surfactant-based sol–gel/ calcination technique.•Co3O4 addition can effectively improve the physicochemical, optical, and photocatalytic properties.•Complete ciprofloxacin photodegradation achieved in 30 min over Co3O4@CeO2.•The degradation rate of 15% Co3O4@CeO2 was 2 times higher than pristine CeO2.•Co3O4@CeO2 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 Co3O4@CeO2 nanocomposite was developed by incorporating different doses (5–20 wt%) of Co3O4 nanoparticles (NPs) using a surfactant-based sol–gel/ calcination technique. The photocatalytic activity of Co3O4@CeO2 nanocomposites was estimated in the degradation of ciprofloxacin (CIP) antibiotic under visible exposure. : Optimizing the Co3O4 mass yields a bandgap semiconductor of 2.66 eV with a wide visible light. The 15% Co3O4@CeO2 nanocomposite displayed the best CIP destruction performance after 45 min, with 2-fold greater activity than pure CeO2 NPs. After 30 min of visible light illumination, 2.4 gL−1 dosage of 15% Co3O4@CeO2 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 Co3O4@CeO2 is postulated based on the effective segregation of photoinduced charge carriers via an S-scheme mechanism, where electron–hole pairs can easily move between CeO2 and Co3O4 because of their matched band locations. This research corroborates the use of nanoheterojunction oxides in rapidly removing antibiotic residues under visible light. [Display omitted]