Microwave responsive copper-ferrite (CuFe2O4) encapsulated in molybdenum-disulfide (MoS2) nanoflower catalyst for antibiotic removal via persulfate oxidation

Abstract

Microwave (MW) responsive copper-ferrite/molybdenum-disulfide (CuFe2O4/MoS2) nanoflower catalyst was implemented for rapid antibiotic metronidazole (MNZ) degradation via persulfate oxidation under MW irradiation. The catalyst was synthesized via co-precipitation followed by hydrothermal methods, and characterized by XRD, FTIR, SEM, TEM, VSM, XPS, and UV-DRS. As a first step, MW induced MNZ removal was studied at different initial mass of CuFe2O4/MoS2 (2.5–20%), where 5% CuFe2O4 in the nanocomposite performed the best. Within 5 min of MW irradiation, 100% MNZ removal was observed (Kobs ∼ 1.063 min−1) under the optimal reaction conditions (i.e., CuFe2O4/MoS2 dose ∼ 0.4 g/L; PS dose ∼ 100 mg/L; temperature ∼ 90 °C; and MW power ∼ 350 W). The MNZ removal was independent of solution pH 3–11, and the removal was by SO4•−and •OH radicals alongside the limited contribution from O2•−. PS and H2O were thermally decomposed to produce SO4•−and •OH radicals, whereas intrinsic semiconductor CFO/MS with a narrow bandgap of 1.53 eV allowed electrons to jump into conduction band from valance band to create SO4•− and O2•−. However, the performance of MW system was inhibited by the presence of anions in the order of Cl−< NO3− <CO32− <H2PO4−. Robustness of the CuFe2O4/MoS2 was proved via recyclability experiments, and MNZ removal was found to be dropped ∼ 4.89% at the end of 5th cycle. It was proposed that the absorbed MW energy was dissipated through various losses to generate ‘hotspots’ (>1200 °C) for MNZ removal. Synergistically, redox couples of transitional metals contributed to MNZ degradation.