Effect of Fe (II) concentration on metronidazole degradation by Fenton process: Performance and Kinetic study

Metronidazole (MNZ) is an antibiotic drug to be carcinogenic and mutagenic. The present work was focused on MNZ degradation using the Fenton process, in batch studies. Five initial concentrations of MNZ (0.5, 5, 10, 15 and 20 mg/L), three Fe (II) concentrations (2.94, 5.88 and 11.66 μM), 29.4 μM H2O2, and three pH (3.5, 5 and 7) were evaluated at a reaction time of 5 min. A statistical factorial design using the program Minitab 18® was used to study the MNZ degradation. The best experimental conditions to degrade MNZ at 100% was 2.94 μM Fe2+ and pH of 3.5. Three kinetic models were used to study the degradation profile of MNZ at 2.94 μM Fe2+ and 29.4 μM H2O2, such as the first-order, the second-order, and BMG kinetic model. The BMG kinetic model was the best model to describe the MNZ degradation by Fenton process. On other hand, the optimal pH for MNZ degradation was 3.5, independently of the molar ratio Fe2+/H2O2 evaluated. At pH 5, degradation efficiencies decreased significantly, while at pH 7 the lowest degradation of MNZ was observed. Finally, the Fenton process showed the potential to degrade metronidazole.