Synthesis of the MnO2-Fe3O4 catalyst support on amorphous silica: a new Fenton's reagent in the degradation of the reactive blue-19 in aqueous solution.

In this study, a new Fenton's reagent was synthesized via two steps: (1) the dispersed Fe₃O₄ nanoparticles were immobilized on the surface of the SiO₂ carrier via the precipitation process, and (2) the MnO₂ nano-sheets were coated on the surface of Fe₃O₄/SiO₂ via hydrothermal method. The SiO₂ carrier has been synthetically utilized from Vietnamese rice husk. The successful formation of the MnO₂-Fe₃O₄/SiO₂ composite has been analytically characterized by the XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive spectrometry)-mapping, FTIR (Fourier transform infrared), S_BET (Brunauer-Emmett-Teller specific surface area), and adsorption/desorption isotherms. This Fenton system was employed to catalyze degradation process of the reactive-blue 19 (RB19) with approximately 100% of removal efficiency after 25 min at the optimal condition of 0.15 g/100 mL of catalyst dosage, pH = 3, and the H₂O₂ concentration of 3 mL/100 mL. Moreover, the catalyst could be reused at least six times with high catalytic activity that was more than 90%. In conclusion, this study showed that the mesoporous MnO₂-Fe₃O₄/SiO₂ composite has a great potential for the removal application of dyes from wastewater, and the application of Vietnam rice husk in environmental treatment was developed.