Combination of ultrasonic and Fenton processes in the presence of magnetite nanostructures prepared by high energy planetary ball mill

High energy planetary ball milling process was used to prepare magnetite nanostructures from natural magnetite. The natural and ball-milled magnetite samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The results of EDX indicated the presence of main elements including Fe and O in the structure of both unmodified and milled magnetite samples. The specific surface area of catalyst increased from 0.9116 m²/g to 28.692 m²/g after ball-milling process. The catalytic activity of prepared magnetite nanostructures was evaluated towards degradation of Acid Blue 185 (AB185) in ultrasonic assisted heterogeneous Fenton reaction. 6 h ball-milled catalyst exhibited the higher catalytic activity in degradation of AB185. The high degradation efficiency was obtained at initial pH of 3. Increasing the concentration of H₂O₂ from an optimum value of 15 mM led to decrease in degradation efficiency because of scavenging effect of H₂O₂ on hydroxyl radicals. The optimized catalyst concentration was obtained 1.5 g/L. Increasing initial dye concentration from 20 to 120 mg/L led to decrease in degradation efficiency from 99 to 88%. The prepared magnetite nanostructures exhibited good stability in repeated cycles. The produced intermediates of the degradation of AB185 in ultrasonic assisted heterogeneous Fenton process were monitored by GC–MS analysis.