Facile synthesis of 3D hierarchical MnO2 microspheres and its ultrahigh removal capacity of organic pollutant
A well defined 3D hierarchical microspheres of MnO2 have been successfuly prepared by simple microwave heating method in just 10 minutes without using any templates, catalysts and organic reagents. As-synthesized MnO2 microspheres are well characterized by using XRD, XPS, BET, SEM, TEM and HRTEM methods. 3D hierarchical MnO2 microspheres have porous structure with high specific surface area (184.32 m2 g-1) and large pore volume (0.416 cm3 g-1). MnO2 microspheres are assembled of ultrathin nanosheets with thickness of around 2 nm. MnO2 microspheres are found to exhibit exceptional catalytic performance in degradation of methyl blue (MB) in aqueous solution, which indicates its strong potential for waste water treatment. It exhibits outstanding catalytic activity to degrade 95 % of MB ( 400 mg/L) within 25 minutes in the presence of H2O2 by a Fenton-like reaction. The weight ratio of degraded MB to MnO2 micropshres (40mg/mg) is the highest amongst all the reported catalysts for MB. MnO2 microspheres also demonstrate efficient performance as a reactive sorbent to degrade 90 % of parathion methyl (organophosphate pesticide) within 100 minutes in non-polar organic solvent (n-heptane). The ultrahigh removal capacity can be ascribed to high specific surface area, porous structure and ultrathin nanosheets building blocks of MnO2 microspheres.