Manganese doped magnetic cobalt ferrite nanoparticles for dye degradation via a novel heterogeneous chemical catalysis

Composite cobalt ferrites doped with manganese were successfully synthesized via sol-gel auto combustion method and were annealed at a temperature of 400 °C. The catalytic activity of a series of catalysts at different manganese contents was studied using the sodium bisulfite-assisted system for degradation of water-soluble organic pollutants such as orange Ⅱ (OⅡ). The obtained ferrite compositions were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM) and X-ray photoelectron spectrometer (XPS). The results showed that the degradation efficiency was greatly enhanced in the presence of NaHSO₃. In addition, all the Mn-containing samples showed much higher capability to degrade OⅡ than the pure CoFe₂O₄ under the same conditions. Among all the samples containing manganese, the CoMn_0.2Fe_1.8O₄ sample showed higher degrading ability. The CoMn_0.2Fe_1.8O₄ sample also showed strong ferromagnetic property with the saturation magnetization and remanence magnetization of 43.1 emu/g and 22.5 emu/g respectively, which is expected to provide a good magnetic separation performance.