Efficient photocatalytic remediation of typical antibiotics in water via Mn3O4 decorated carbon nitride nanotube

Abstract

Antibiotic abuse will seriously affect the ecology and environment. Photocatalytic oxidation technology based on carbon nitride (g-C₃N₄) has been widely adopted to treat wastewater containing antibiotics. Here, a novel composite photocatalyst MCNT was prepared by loading manganese oxide (Mn₃O₄) on the surface of g-C₃N₄ nanotubes (CNT). Three typical antibiotics, trimethoprim (TMP), norfloxacin (NOR), and tetracycline (TC) were used as model contaminants to evaluate the oxidative properties of prepared materials. Compared with bulk g-C₃N₄, the degradation rates of TMP, NOR, and TC catalyzed by MCNT-5 were increased by 2, 3, and 1.4 times, respectively, mainly due to 1) the larger specific surface area of the nanotube structure of CNT, which provides abundant active sites for antibiotic adsorption and catalytic oxidation, and 2) the loading of Mn₃O₄, which promotes the directional migration of photogenerated charges and improves the separation efficiency of photogenerated electrons and holes. The free radical capture and quenching experiments confirmed that MCNT degraded the target organic pollutants with hydroxyl radical (·OH) and singlet oxygen (¹O₂) as the main active oxidants. This catalyst maintained 80% photocatalytic oxidation performance after five cyclic experiments. This study provides new insights into developing efficient, stable, and environmentally-friendly photocatalysts and provides a new dimension to mitigate the antibiotic pollution problem.

Keywords: Antibiotics; Carbon nitride nanotube; Free radicals; Manganese oxide; Photocatalysis.