Facile Synthesis of Monodisperse Manganese Oxide Nanostructures and Their Application in Water Treatment

Different manganese oxide nanomaterials were prepared by treating their precursor, which had been prepared by mixing KMnO 4 solution and oleic acid at room temperature, at low temperatures (≤200 °C). While the hierarchical morphology was kept, the phase structure was transformed from layered manganese oxide to tetragonal hausmannite. The manganese oxide nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and nitrogen adsorption−desorption measurements. These nanostructures showed better adsorption capacity of organic polluents (methylene blue) than existing MCM-22, Red mud, and other synthesized manganese oxide (including α-, β-, and γ-) materials. The adsorption capacity of the nanomaterials did not largely depend on their surface area. The possible adsorption mechanisms are also discussed.