Fast and efficient removal of metronidazole from aqueous solution using graphene oxide (GO) supported nitrogen (N) doped zinc oxide (ZnO) nanoparticles

This work focused on the preparation of ZnO nanoparticles through modifications by nitrogen incorporation (N-ZnO NPs) and thereafter immobilized them on graphene oxide (GO) nanosheets to form GO-N-ZnO nanocomposites, followed by its application for the removal of metronidazole (MNZ) antibiotic from aqueous solution by effective adsorption and visible light driven photocatalysis. The structural, functional, surface morphology and optical properties of the synthesized samples were investigated by numerous techniques. In the comparative study of catalytic degradation of MNZ, GO-N-ZnO demonstrates 96.6% removal efficiency from aqueous solution by adsorption and photocatalysis under visible light irradiation and corresponding degradation kinetics have been studied. Thereafter, effects of initial concentration of MNZ and GO-N-ZnO catalyst dosages have been investigated. Scavengers test reveals that superoxide radicals are responsible for such fast improved degradation. A possible explanation is provided for such fast improved degradation of MNZ by GO-N-ZnO catalyst. The reusability and stability tests demonstrate that as prepared GO-N-ZnO can be used up to fourth consecutive cycles with satisfactory removal efficiency (88.4%) and retains its crystal structure. Finally, microbiological assay showed that the degraded MNZ aqueous solution has diminished capacity to inhibit bacterial growth compared to the control MNZ solution. These results describe the potential of environmental-friendly GO-N-ZnO catalyst for remediation and long-term reusability. [Display omitted] •High yield GO supported N-doped ZnO nanoparticles are synthesized by cost-effective route.•GO-N-ZnO demonstrates band gap narrowing with strong visible light absorption.•Adsorption capacity of GO-N-ZnO is as high as 60.10 mg/g.•Faster and enhanced photocatalytic performance under visible light illumination.•Reusable up to 4th consecutive cycles retaining 88.4% degradation efficiency.