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 KMnO4 solution and oleic acid at room temperature, at low temperatures (<= 200 degrees 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 alpha-, beta-, and gamma-) materials. The adsorption capacity of the nanomaterials did not largely depend on their surface area. The possible adsorption mechanisms are also discussed.