Catalytic ozonation of antibiotics by using Mg(OH)2 nanosheet with dot-sheet hierarchical structure as novel nanoconfined catalyst

Abstract

Antibiotic pollution has caused important concern for international and national sustainability. Catalytic ozonation is a quick and efficient technique to remove contaminants in aquatic environment. This study firstly developed a nanosheet-growth technique for synthesizing Li-doped Mg(OH)2 with dot-sheet hierarchical structure as catalyst to ozonize antibiotics. Metronidazole could be totally removed through ozonation catalyzed by Li-doped Mg(OH)2 in 10 min. Approximately 97% of metronidazole was eliminated in 10 min even the catalyst was used for 4 times. Reaction rate constant of Li-doped Mg(OH)2 treatment was about 3.45 times that of nano-Mg(OH)2 treatment, illustrating that the dot-sheet hierarchical structure of Li-doped Mg(OH)2 exhibited nano-confinement effect on the catalytic ozonation. Approximately 70.4% of metronidazole was mineralized by catalytic ozonation using Li-doped Mg(OH)2. Temperature of 25 °C was more suitable for catalytic ozonation of metronidazole by Li-doped Mg(OH)2. Ions generally inhibited the catalytic ozonation of metronidazole while only 0.005 mol L−1 of Cl− slightly enhanced the ozonation rate, illustrating complicated mechanisms existed for ozonation of metronidazole catalyzed by Li-doped Mg(OH)2. The possible mechanisms of the ozonation of metronidazole using Li-doped Mg(OH)2 included direct ozonation and ozonation catalyzed by radical ·O2−, reactive oxygen species 1O2 and intermediate (H2O2). The synthesized Mg(OH)2 nanosheet with dot-sheet hierarchical structure is a novel nanoconfined material with excellent reusability and catalytic performance.