Abstract:

：Layered manganese dioxide（δ-MnO₂） and tunneling manganese dioxide（α-MnO₂） nanomaterials were prepared by using hydrothermal oxidation-reduction reaction by using KMnO₄ as oxidant and（NH₄）₂ Fe（SO₄）₂ as reductant.The obta-ined products were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and N₂ adsorption-des-orption technologies in order to investigate their crystalline,morphology and pore structural properties.The above results indi-cate that δ-MnO₂ has flower-like sphere morphology with mesoporous structure（average pore diameter is 3.4 nm）,and its BET specific surface area is 219 m²/g.α-MnO₂ has nanowire bundles shape with partial mesopore structure（average pore di-ameter is 35.7 and 154.6 nm）,and its BET specific surface area is 26 m²/g.In addition,the adsorption properties of methylene blue on different crystalline of manganese dioxide were studied which demonstrate that the adsorption performance of α-MnO₂ was better than that of δ-MnO₂ under the same conditions,and the absorption efficiency was even better in alkaline environ-ment.When the reaction time reached 120 min,the removal rates of α-MnO₂ and δ-MnO₂ toward methylene blue reach to 84.4% and 82.9%,respectively.

Key words: manganese dioxide, crystalline, morphology, adsorption, methylene blue