The Solid-state Synthesis of MnFe₂O₄ and its Application as Photo-Fenton Catalyst for the Degradation of dye

Abstract Manganese ferrite spinel has been successfully synthesized using birnessite-type manganese oxide (MnO 2 ) and ferric chloride (FeCl 3 ) through solid-state method. The solid product was then calcined at different temperatures to study the effect of the calcination on the structure and catalytic activity. The as-synthesized ferrite was further characterized by XRD, FTIR and Raman spectroscopy, and UV-DRS spectroscopy. The XRD results revealed that the predominant phase present is MnFe 2 O 4 , with the cyptomelane-type MnO 2 appearing as a minor components. The increase in the calcination temperature resulted in more crystalline phase and purity of MnFe 2 O 4 . The IR vibration modes are found in-between 432-745 cm −1 with Fe-O bond at 680 cm −1 and 745 cm −1 , and Mn-O at 412 cm −1 , 432 cm −1 and 488 cm −1 indicated the spinel phase of the MnFe 2 O 4 . The Raman results further confirmed the presence of the MnFe 2 O 4 phase. The UV-DRS results indicated that the calcination temperature has a strong influence on the optical properties. The catalytic test was conducted for the degradation of methylene blue (MB) dye using the photo-Fenton method and the MnFe 2 O 4 calcined at 700°C showed the highest catalytic activity. In the optimum condition, the MnFe 2 O 4 was able to degrade 97.99% of MB with the following conditions: 0.04 g of MnFe 2 O 4 , 5 mL of H 2 O 2 , and 50 ppm of initial MB concentration. The optimum condition seems to correlate with a low band gap and high purity of the MnFe 2 O 4 phase.