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

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.