Synthesis of MnO2 nanosheets on montmorillonite for oxidative degradation and adsorption of methylene blue.

In this research, MnO2 nanosheets on montmorillonite (MnO2 nanosheets@MMt) was synthesized by one-pot hydrothermal method and characterized by X-ray diffraction, Fourier transform infrared spectra, nitrogen adsorption and scanning electron microscopy. It was found that honeycomb-like MnO2 nanosheets vertically grew on the surface of montmorillonite. MnO2 nanosheets@MMt exhibited high methylene blue (MB) removal rate, which reached 97.7% within 5min under the condition of pH 2, MnO2 nanosheets dosage of 0.1gL-1 and initial dye concentration of 10mgL-1. Additionally, the influencing factors such as pH value, amount of MnO2 nanosheets@MMt, and MB concentration were also investigated in this paper. Results showed the MB degradation process was correlated with pH value, and the MnO2 nanosheets@MMt achieved MB removal rate of 92.8% within 5min under pH 11 because of its absorption capacity of MB. The kinetics of the adsorption process complied with the Pseudo-second-order model. The Langmuir model was found to be the most suitable for describing the experimental equilibrium data of MnO2 nanosheets@MMt. The MnO2 nanosheets@MMt showed high adsorption capacity of 363.63mgg-1 for MB dye. The oxidative decomposition of MB was conducted in the presence of MnO2 nanosheets@MMt in the low pH, finding that the lower the pH was, the faster the degradation rate was. This research demonstrates that MnO2 nanosheets@MMt has potential applications in wastewater treatment.