MnZn ferrite synthesized by sol–gel auto-combustion and microwave digestion routes using spent alkaline batteries

Abstract The combination of a sol–gel auto-combustion method and a microwave digestion method was used to synthesize nanocrystalline MnZn ferrite powders using spent alkaline batteries. The overall process involved four steps: dissolution of spent batteries; the sol–gel formation; MnZn ferrite precursor powder formation; MnZn ferrite powder formation. The products were characterized for phase composition, morphology, and magnetic properties by inductively coupled plasma optical emission spectroscopy (ICP-OES), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and vibrating sample magnetometer (VSM) techniques. IR spectra and DTA/DSC studies revealed that the combustion process is an oxidation–reduction reaction in which the NO 3 − ion is the oxidant and the citric acid is the reductant. Nanocrystalline MnZn ferrite powders were successfully prepared by a microwave digestion method using MnZn ferrite precursor powders at 120 °C for 15 min. The results obtained showed the formation of single-phase MnZn ferrite powders with an average particle size of about 50 nm. The results further revealed that microwave digestion conditions had a greater influence on the magnetic properties of the MnZn ferrite powders than the sol–gel auto combustion process alone.