Hydrothermal synthesis of Mn-Zn ferrites from spent alkaline Zn-Mn batteries

Nanocrystalline Mn–Zn ferrites (Mn_0.6Zn_0.4Fe₂O₄) with particle size of 12 nm were synthesized hydrothermally using spent alkaline Zn–Mn batteries, and accompanied by a study of the influencing factors. The nanocrystals were examined by powder X-ray diffraction (XRD) for crystalline phase identification, and scanning electron microscopy (SEM) for grain morphology. The relationship between concentration of Fe(II), Mn(II), and Zn(II) and pH value was obtained through thermodynamic analysis of the Fe(II)–Mn(II)–Zn(II)–NaOH–H₂O system. The results showed that all ions were precipitated completely at a pH value of 10–11. The optimal preparation conditions are: co-precipitation pH of 10.5, temperature of 200 °C and time of 9 h.