Synthesis and Application of Chitosan–Graphene Oxide and Titanium-Dioxide Coated Granular Activated Carbon Composites for Adsorptive and Photocatalytic Removal of Antibiotics

Abstract

The main aim of this study was to remove a model antibiotic, that is, metronidazole (MET), using TiO2 coated on granular activated charcoal (GAC–TiO2) and graphene oxide (GO) embedded in chitosan (CS) by adsorption and photocatalysis. Analyses including scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Fourier transform Ramen spectroscopy, X-ray diffraction, and the BET method, along with batch adsorption and photocatalysis results, were used to compare the performance of composites. The ultraviolet C (UVC)/CS–GO system (99.4%) showed higher MET removal compared with UVC/GAC–TiO2 (97.4%) at 10 mg L−1 initial MET concentration; however, the total organic carbon reduction was greater in the GAC–TiO2 system (78.4%) than in the CS–GO system (72.3%). After 120 min, the UVC/GAC–TiO2 and UVC/CS–GO systems showed maximum MET removal rates of 0.0561 and 0.04 min−1, respectively. By contrast, batch adsorption experiments indicated that CS–GO has approximately 20 times greater MET adsorption capacity than GAC–TiO2. Furthermore, CS–GO was found to be superior in MET removal than GAC–TiO2 in a reusability study (i.e., for 15 treatment cycles), owing to higher adsorption capacity. Overall, the results indicate that CS–GO could be a potential composite for continuous photocatalytic experiments in the framework of emerging contaminant removal.