Synthesizing Fe3O4, Mn3O4 and Mn3O4/Fe3O4 nanocatalysts using the sol-gel method as new precursors for the degradation of phenol by catalytic ozonation

Ozone has received much attention in wastewater treatment as an impressive oxidation agent. In this work, three new metal complexes, [pyda.H][Fe(pydc)(pydc.H)].H2O, (I); [pyda.H][Fe(pydc)2].H2O, (II); and [pyda.H2]5[Mn(pydc.H)2].[pydc]5.8H2O, (III), where [pyda.H]+ = 2,6 -diaminopyridinium and [pydc]2- = 2,6 -pyridinedicarboxylate, have been synthesized by the ultrasonic-assisted synthesis method and then characterized by field emission scanning electron microscope (FE-SEM), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric (TGA), and elemental analyses. According to the SEM image, the morphology of compound III was a nanorod. Compounds I, II, and III were then used as precursors for the preparation of Fe3O4, Mn3O4, and Mn3O4/Fe3O4 using the sol-gel and impregnation methods, respectively. Characterization of the synthesized nano-catalysts was carried out by FE-SEM, X-ray powder diffraction (XRD), and energy diffraction X-ray (EDX), the vibrating sample magnetometer (VSM) was replaced by magnetic studies. The VSM result showed that Fe3O4 and Mn3O4/Fe3O4 were superparamagnetic and ferromagnetic compounds, respectively. The Mn3O4, Mn3O4/Fe3O4, and Fe3O4 nanocatalysts were applied for the decomposition of phenol in an aqueous solution by catalytic ozonation. Phenol degradation efficiency was obtained as 97.26, 97.74, and 88.62 %, respectively.