Fabrication, characterization of β-MnO2 microrod catalysts and their performance in rapid degradation of dyes of high concentration

Abstract

Under hydrothermal conditions, a series of β-MnO2 microrod catalysts were fabricated using different manganese precursors (MnSO4, (CH3COO)2Mn·4H2O, MnCl2·4H2O, Mn(NO3)2·4H2O). The as-prepared β-MnO2 microrods were characterized by powder X-ray diffraction (XRD), N2 physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The characterization results showed that the morphologies and crystallinity of MnO2 were mainly determined by the hydrothermal time and temperature. Suitable hydrothermal time and temperature produced well defined β-MnO2 microrods with high crystallinity. The obtained β-MnO2 microrod catalysts were applied to degrade different dyes with high concentration (methylene blue (MB), methyl orange (MO), rhodamine B (RB) and acid orange II (AOII)) in the presence of H2O2. The catalytic mechanism was discussed and a Fenton-like reaction mechanism was proposed. High crystallinity and good morphology effectively promoted the catalytic performance of β-MnO2 microrods. The efficiencies of β-MnO2 microrods in degradation of different dyes are markedly different. The dye degradation rates followed the order of MB>AOII>RB>MO. Moreover, the β-MnO2 microrods exhibited high stability in recycling degradation, which suggests promising applications in practical dye pollutant treatment.