This study aims to investigate the efficacy of photocatalytic and Fenton-like photocatalytic processes using the FeNi3/SiO2/CuS nanocomposite in the removal of metronidazole (MNZ) from aqueous solutions in the presence of ultraviolet (UV) light. The desired magnetic nanocomposite was first synthesised and then characterised using electron microscopy (TEM), x-ray diffraction device (XRD), fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), energy dispersive spectroscopy (EDS), and scanning electron microscopy (FESEM). The effects of various physicochemical parameters on the degradation process like the initial MNZ concentrations, the nanocomposite dose, the hydrogen peroxide (H2O2) concentrations, the contact time, and the pH were investigated. According to TEM and FESEM analyses, it was found that the obtained nanoparticles tend to accumulate due to their magnetic properties; hence, the particle size (about 52 nm) was greater than that obtained from the Scherrer equation in the XRD analysis. VSM analysis results revealed that the studied nanocomposite was dispersed in water and could be easily separated by an external magnetic field in a short time, and then be easily re-dispersed with shaking slightly. The maximum removal efficiency was obtained by an exposure time of 200 min, pH of 7, MNZ concentration of 20 mg/L, and a catalyst dosage of 0.02 g/L in the photocatalytic degradation stage. Optimum conditions in the Fenton-like photo-catalytic stage were a pH of 7, a time of 180 min, MNZ concentration of 20 mg/L, a catalyst dose of 0.01 g/L, and an H2O2 concentration of 150 mg/L. The photocatalytic degradation of MNZ has followed the pseudo-first-order kinetic model. Results of catalyst recovery and recycling tests showed that the synthesised nanocomposite had a very high recovery and recycling capacity, with only a 5.05% reduction in contaminant degradation efficiency after six alternating cycles. In the Fenton-like photo-catalytic degradation stage, the difference of catalyst degradation percentage was very small among the cycles, showing a decrease of 2.84% from the first to the last cycles. Therefore, the magnetic nanocomposite synthesised in the photocatalytic and heterogeneous Fenton-like photocatalytic degradation of MNZ can be used as a suitable catalyst in the removal and degradation of resistant organic drugs contaminants.
