Heterogeneous catalytic degradation of phenol by a Fenton-type reaction using copper ferrites (CuFe₂O₄)

The potential application of copper ferrite (CuFe₂O₄) as a heterogeneous catalyst in the process of phenol degradation was investigated using high performance liquid chromatography (HPLC). CuFe₂O₄ nanoparticles were synthesized by sol-gel auto combustion and co-precipitation methods, and subsequently were calcined at 500°C and 750°C. The prepared ferrites were characterized for their morphology, crystallinity, purity, and stability using various techniques such as X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and BET surface area analysis. The sol-gel derived CuFe₂O₄ particles exhibited spinel phases of higher porosity and crystallinity as well as higher catalytic activity toward the degradation of phenol. Calcination of CuFe₂O₄ resulted in larger particles of higher purity and crystallinity, but of lower catalytic activity towards the degradation of phenol. The catalytic activity of the sol-gel CuFe₂O₄ was compared with the activity of two other sol-gel prepared ferrite catalysts, zinc ferrite (ZnFe₂O₄) and magnesium ferrite (MgFe₂O₄) catalysts, and with a commercial titanium dioxide (TiO₂) catalyst. Among these catalysts, HPLC results demonstrated that CuFe₂O₄ exhibited the highest catalytic activity towards the degradation of phenol. Furthermore, the effects of several experimental parameters on the degradation rate of phenol over CuFe₂O₄ were investigated including the solution pH, reaction temperature, H₂O₂ concentration, catalyst loading, H₂O₂ addition mode, stirring, and the presence of UV or sunlight radiations. The degradation rate was enhanced by increasing the H₂O₂ concentrations, the CuFe₂O₄ catalyst loadings, or the reaction temperature. A faster and complete removal of phenol was observed under acidic conditions or under the presence of UV or sunlight radiation. CuFe₂O₄ was successfully regenerated and reused for five degradation cycles without noticeable loss in its activity.