In this work, the activity of NiFe2O4 and ZnFe2O4 photocatalysts as single and heterostructure semiconductor nanoparticles was studied toward metronidazole (MZ) in an aqueous solution. This drug, which is one of the widely used drugs, is easily dissolved in water and is a water pollutant, so it is necessary to remove it from the wastewater. The coprecipitation method was used for the synthesis of the catalysts. FTIR, SEM-EDX, X-ray mapping, DRS, and VSM techniques were applied to characterize the samples’ XRD. Crystallite sizes for ZnFe2O4, NiFe2O4, and Zn0.75Ni0.25Fe2O4 obtained with the Scherrer formula are about 4.6, 10.1, and 21.6 nm, while by the Williamson-Hall formula are about 3.7, 4.3 and 21.1 nm, respectively. FT-IR spectra of all samples show two prominent absorption bands near the frequency range 400 and 600 cm-1 belonging to the Fe-O (or M-O) bond at octahedral and tetrahedral, respectively. Obtained EDX results confirm that the ZnFe2O4: NiFe2O4 mole ratio of 3:1, and constituent particles are normal distribution in Zn0.75Ni0.25Fe2O4. The band gap energy was estimated. The VSM results confirm that ZnFe2O4, NiFe2O4 and Zn0.75Ni0.25Fe2O4 photocatalysts have magnetic properties. The simultaneous effects of the experimental variables were evaluated by central composite design combined (CCD) with a response surface methodology (RSM) approach. The quadratic model has a high correlation coefficient (R2 = 0.9820), which indicates a good match between the predicted data and the experimental results. 92.9 % mineralization of metronidazole was obtained for the run with specifications, pH 5, 0.8 g L-1 for the catalyst dose, 5 mg L-1 for metronidazole concentration, and 70 min for irradiation time. The catalyst used in this research has the standard potential and capacity for proper conductivity levels and better e-/h+ separation. It has reduced recombination and increased degradation efficiency.
