Facile decolorization of methylene blue with flower-like manganese wads

Flower-like manganese wads (MWs) were synthesized via a simple and inexpensive ultrasonic irradiation method for the first time. MWs were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and transmission electronic microscopy. The decolorization efficiency of MWs for methylene blue (MB) azo dye was examined as a function of pH, stirring time, MW dosage and initial concentration of the MB solution. Results show that MWs have excellent decolorization performance for MB with a higher efficiency (and without using H₂O₂ or other devises such as UV light and ultrasonic irradiation) compared to other catalysts, such as the mixture of Mn₃O₄ and H₂O₂ (with a maximum decolorization rate of 99.7% in 3 h), ZnS and CdS under light irradiation (with a maximum decolorization rate of 73% in 6 h), and sulfate modified titania under solar radiation (with a maximum decolorization rate of nearly 100% in 4 h).