Synergistic degradation of metronidazole and penicillin G in aqueous solutions using AgZnFe2O4@chitosan nano-photocatalyst under UV/persulfate activation

Abstract

In recent years, the persistence of pharmaceutical contaminants like metronidazole (MNZ) and penicillin G (PG) in water bodies has become a major environmental concern. The present research studied the simultaneous degradation of MNZ and PG utilizing an AgZnFe2O4@Ch catalyst generated through the co-precipitation technique as an effective stimulator for persulfate (PS) in the existence of UV light. The structure of the AgZnFe2O4@Ch catalyst was characterized using X-ray powder diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, vibrating-sample magnetometer, and energy dispersive spectroscopy mapping. After 50 minutes of reaction time under the ideal operating conditions, which included 0.4 g/L of catalyst, 4 mM of PS, 5 mg/L of MNZ and PG, and a pH of 5, the highest MNZ and PG degradation of 81.5 % and 82.3 % were obtained. Statistical parameters, including the R2 values of 0.985 for MNZ and 0.981 for PG, indicate a very good agreement between the predicted and observed values. The Garson's method analysis revealed that PS dosage had the greatest impact on MNZ degradation, while the initial concentration of PG exerted the most significant influence on PG degradation. The Langmuir-Hinshelwood model has surface reaction rate constants (Kc) of 0.954 (mg/L.min) and adsorption equilibrium constants (KL-H) of 0.032 (L/mg) for both antibiotics, respectively. The claimed mechanism was illustrated by the free radical scavenging studies, which demonstrated that the SO•4- radicals were the main radicals involved in the degradation of MNZ and PG. A last investigation of the catalyst's regeneration revealed that it had satisfactory chemical stability after five cycles of usage and regeneration using chemical approaches.