Photocatalysis assisted by activated-carbon-impregnated magnetite composite for removal of cephalexin from aqueous solution

Abstract

The simultaneous presence of antibiotics and bacteria in aqueous media has been recognized as an environmental threat, due to the enhancement of antibiotic resistance of bacteria. We synthesized an activated carbon impregnated magnetite composite (PAC/Fe3O4) and used it for removal of cephalexin (CEX) from aqueous solution via UV system. A series of batch experiments was carried out under various experimental conditions such as pH of solution (3–11), contact time (0–120 min), catalyst dosages (0.1–2 g/L) and initial CEX concentrations (10, 25, 50 and 100 mg/L). Some common isotherm models were used for study of CEX adsorption and finding the best model. In addition, kinetic studies of CEX photocatalytic removal were performed by fitting the experimental data on first-order and second-order models. Results of comparative studies showed that UV+PAC/Fe3O4 and UV+TiO2 systems, compared to UV/Fe3O4, naked Fe3O4, PAC/Fe3O4 and UV only, had more capability of removing CEX from aqueous solution, indicating PAC/Fe3O4 is effectively catalyzed by UV light. Furthermore, increasing catalyst dosages and decreasing initial CEX concentrations led to the enhancing photocatalytic removal of CEX from solution. The obtained results of kinetic studies also represent that among the studied models, second-order model with significant coefficient of correlation (R2) had higher ability than first-order model to fit the data of CEX removal. Finally, the findings of reusability tests, showed that the applied catalyst would be applicable for CEX removal, even after five consecutive cycles.