Enhanced activation of persulfate by CuCoFe2O4@MC/AC as a novel nanomagnetic heterogeneous catalyst with ultrasonic for metronidazole degradation

In this study, the degradation of Metronidazole (MNZ) using CuCoFe2O4@MC/AC catalyst synthesized by microwave-assisted method, as an efficient activator for persulfate (PS) in the presence of ultrasonic (US: 60 kHz) was investigated. X-ray powder diffraction (XRD), Field emission scanning electron microscope (FESEM), Energy dispersive spectroscopy (EDS)-Mapping and Line scan, Fourier transform infrared spectroscopy (FTIR), Vibrating-sample magnetometer (VSM), and Thermal gravimetric analysis (TGA) were conducted to characterize the structure of CuCoFe2O4@MC/AC catalyst and then the catalyst dose, PS dose, MNZ concentration, and pH parameters were optimized. The maximum MNZ degradation of 93.78 % was achieved after 15 min reaction at the optimized operation conditions: 0.4 g L−1 of catalyst, 6 mM of PS, 5 mg L−1 of MNZ, and pH of 3. The removal efficiency of Total Organic Carbon (TOC) was 87.5 % under optimal conditions. According to kinetic equations, it was found that the MNZ degradation followed both kinetics (pseudo-first-order and Langmuir-Hinshelwood) based on the coefficient of determination (R2) of 0.949, 0.9716, 0.9073, 0.9721, and 0.9662 at concentrations of 5, 10, 15, 20, and 30, respectively. The surface reaction rate constant (Kc) and the adsorption equilibrium constant (KL-H) of the Langmuir-Hinshelwood model were 0.81 (mg L−1 min−1) and 2.184 (L mg−1), respectively. The free radical scavenging experiments were conducted to illustration the proposed mechanism, which shown that the SO4−• was the predominant radicals involved in MNZ degradation. Finally, the regeneration of the catalyst was investigated and showed that after five cycles of use and regeneration by chemical and thermal methods, this catalyst has acceptable chemical stability.