Abstract

The presence of emerging contaminants (ECs) such as antibiotics in water bodies has raised increasing concern since they are continuously introduced in aquatic ecosystem and may cause unpredictable environmental hazards and risks, even at trace concentrations. Conventional water treatment processes are known to be generally inadequate for the elimination of these persistent contaminants. As an alternative to conventional biological water treatment processes, photocatalytic degradation of antibiotics has been identified as a promising technique, as it may lead to the mineralization of contaminants into carbon dioxide, water and mineral acid. However, high energy consumption, fast recombination of photo-generated charges, low stability and difficulty in the separation of photocatalysts from treated solution are the main limitations of this process. Herein, to address these obstacles, a low energy consuming photoreactor was designed and built. Besides, the efficiency of process was improved by fluorination and exfoliation of synthesized hierarchical photocatalysts with magnetic properties based on ZnO and graphitic carbon nitride (g-C3N4) as a wide and narrow band gap photocatalyst, respectively. The synthesized photocatalysts were characterized by several characterization tests. The effect of operating parameters such as catalyst dosage, solution pH and airflow rate on the antibiotics removal efficiency and the optimization of process was studied by response surface methodology (RSM). Under the optimum conditions, the photocatalytic removal performance was examined in terms of sulfamethoxazole (SMX), ampicillin (AMP) and amoxicillin (AMX) removal and mineralization as well as detoxification of the solution and by-product formation. Moreover, the reaction kinetics, energy consumption, stability and reusability of photocatalysts were evaluated. Based on the LC-HR-MS/MS method, the formation of several by-products during the degradation of antibiotics was evaluated and a degradation pathway for SMX and AMX was proposed. The results showed that in comparison with a 500 W visible lamp, using a UV lamp (10 W) was considerably more effective for AMX removal, its mineralization and detoxification of the solution. Compared to reported values in the literature, the removal efficiency, mineralization, detoxification and energy consumption for the removal of examined antibiotics were improved in this study.