This work aimed to investigate the efficient reduction of methylene blue (MB) by a heterogeneous magnetic nanoparticles/copper (MNs/Cu) Fenton-like catalyst. The MNs/Cu was successfully synthesized in the presence of Citrus aurantifolia extract. The characterizations showed an effective fabrication of Cu onto the surface of MNs. The reduction
of MB by the MNs/Cu Fenton-like catalyst presented an efficiency of 99.5% at the optimum conditions, including MNs/Cu dose of 0.1 mg, temperature of 25°C, contact time of 75 min, pH 4.0, and 20 mL H2O2 30%, MB initial concentration of 25 mg/L. The reduction kinetics was well fitted to pseudo-second-order with reaction rate constant of 0.0029 g/mg.min. The main mechanism of the MB reduction due to active oxygen species was pointed out. The decrease of reduction yield at high pH, catalyst dose and MB concentration was elucidated in this study.