Synthesis and Characterization of Single‐Crystalline MnFe 2 O 4 Ferrite Nanocrystals and Their Possible Application in Water Treatment

Manganese ferrite (MnFe 2 O 4 ) nanospheres and nano‐octahedra with a narrow size distribution were synthesized by a simple solvothermal method. Here, potassium permanganate (KMnO 4 ) was used as reactant and oxidant for the synthesis of MnFe 2 O 4 ferrite nanocrystals. With the use of hydrazine hydrate, the oxidation rate of ferrous ions was kept under control, and the particle size of MnFe 2 O 4 was limited. The results of control experiments reveal that alkalinity and type of solvent are important factors affecting the morphology and crystallization of MnFe 2 O 4 nanocrystals. Both of the as‐prepared samples exhibit ferromagnetic behavior at room temperature. Especially, the saturation magnetization of MnFe 2 O 4 nanospheres with 50 nm diameter is 79 emu/g, which is among the best values reported so far. The nanoparticles also showed good performance in removal of pollutants like Congo red, Cr VI , and Pb II from water by adsorption, even at neutral pH.