Photocatalytic degradation of the antibiotic ciprofloxacin by ZnO nanoparticles immobilized on a glass plate

Nano-photocatalysis is an advanced oxidation process used to degrade resistant organic compounds. This study was undertaken to investigate photocatalytic degradation of the antibiotic ciprofloxacin (CIP) by zinc oxide (ZnO) nanoparticles immobilized on a glass plate in aqueous solution. The resulting nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and pull-off adhesion testing. The parameters influencing removal that were investigated were pH, ZnO concentration, CIP concentration and contact time. Experiments were also conducted under optimal conditions on wastewater from a hospital in the city of Kerman. The results of XRD and SEM indicated that the ZnO immobilized on a glass plate was highly pure and uniform in size (60-70 nm). The results of the pull-off adhesion test was 4.1 MPa. Optimum conditions were pH: 11, reaction time: 90 min, ZnO concentration on the plate: 0.6 g/ L and initial concentration of CIP: 3 mg/ L. The maximum removal achieved was 98.36% and 90.25% for the synthetic solution and hospital wastewater, respectively. The photocatalytic degradation was linearly plotted and was found to follow pseudo-first-order degradation kinetics and was consistent with the Langmuir-Hinshelwood mode. The experimental data was analyzed using the Langmuir and Freundlich models of adsorption. The equilibrium data fitted well with the Freundlich model. Thermodynamic studies showed that adsorption was an exothermic process. Nano-photocatalysis using ZnO immobilized on a glass plate showed relatively high efficiency in removing ciprofloxacin from aqueous solutions and can be recommended for such purposes.