Rapid Decolorization of Methyl Blue in Aqueous Solution by Recyclable Microchannel-like La0.8K0.2FeO3 Hollow Microfibers

Abstract

A novel catalyst of microchannel-like La0.8K0.2FeO3 hollow microfibers for methyl blue (MB) decolorization in aqueous solution via the catalytic wet air oxidation (CWAO) process was prepared by the citrate–gel process. The microchannel-like La0.8K0.2FeO3 hollow microfibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), nitrogen adsorption–desorption, and X-ray photoelectron spectroscopy (XPS) methods. The hollow microfibers have a diameter of about 2 μm, length of tens of micrometers, and hollow structure, and the ratio of hollow diameter to fiber diameter is around 0.5. There are at least two kinds of oxygen species on the hollow microfibers according to XPS analysis. The results show these microfibers have a high activity for MB decolorization and most MB can be decolorized in about 30 min under ambient conditions. The rapid decolorization of MB by La0.8K0.2FeO3 hollow microfibers is largely due to the unique microchannel-like structure of the microfibers and active oxygen on the microfiber surface. The MB decolorization data follow well with the second-order reaction model, and the calculated activation energy for MB decolorization process by the Arrhenius equation is 14.27 kJ/mol. The catalytic activity of the microfibers did not exhibited an obvious degradation after cycling ten times.