Enhanced Degradation of Metronidazole (MNZ) in Aqueous Solutions Using Combined Ultrasonic, Hydrogen Peroxide, and Peroxymonosulfate Processes

Background: Metronidazole (MNZ) is a widely used pharmaceutical compound that has recently emerged as a significant environmental contaminant. Due to its potential mutagenic properties, MNZ poses risks of DNA damage and carcinogenesis. Methods: This experimental study was conducted at the laboratory scale to investigate the efficiency of MNZ removal in aqueous solutions using a novel combination of ultrasonic waves (US), hydrogen peroxide (H₂O₂), and peroxymonosulfate (PMS). Results: In the US/PMS/H2 O2 process, the removal efficiency ranged from 4.3% to 99.5% under the best conditions (PMS dose=6 mmol/L, H2 O2 dose=20 mmol/L, time=30 min, US power=120 W, MNZ concentration=2 mg/L). A comparative analysis of the maximum removal efficiency between the two processes showed that incorporating US significantly increased MNZ removal, resulting in a 3-fold increase in efficiency under different conditions. Furthermore, in the PMS/H₂O₂ process, the H₂O₂ dose exerted the most pronounced impact, followed sequentially by reaction time, PMS dosage, MNZ concentration, and pH. In the US/PMS/H₂O₂ process, reaction time was identified as the most influential factor, followed by MNZ concentration, PMS dosage, US power, and H₂O₂ dosage. The results of the Taguchi design model further underscored the substantial contribution of ultrasonic irradiation to MNZ removal. Conclusion: Overall, the findings demonstrate that US treatment is highly effective at significantly reducing MNZ concentrations in water and wastewater, highlighting the critical importance of parameter optimization in developing efficient US-based treatment technologies.