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

Under hydrothermal conditions, a series of beta-MnO2 microrod catalysts were fabricated using different manganese precursors (MnSO4, (CH3COO)(2)Mn.4H(2)O, MnCl2.4H(2)O, Mn(NO3)(2).4H(2)O). The as-prepared beta-MnO2 microrods were characterized by powder X-ray diffraction (XRD), N-2 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 beta-MnO2 microrods with high crystallinity. The obtained beta-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 beta-MnO2 microrods. The efficiencies of beta-MnO2 microrods in degradation of different dyes are markedly different. The dye degradation rates followed the order of MB > AOII > RB > MO. Moreover, the beta-MnO2 microrods exhibited high stability in recycling degradation, which suggests promising applications in practical dye pollutant treatment. (C) 2013 Elsevier B.V. All rights reserved.