MnO2 nanorods were prepared by the reaction of KMnO4 and MnSO4 in aqueous media and subsequently followed by hydrothermal methods. The structure and surface morphology of as-prepared powder were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results indicated that the prepared MnO2 possessed α- and γ structure. SEM observations showed that the obtained MnO2 powder possessed a well-defined one-dimensional nanorod-like shape 100 nm wide and 700 nm long. The surface area of the MnO2 nanorods was 92 m2 g−1. The degradation efficiency of MnO2 nanorods towards the organic pollutants in aqueous solution was evaluated using acid orange II as a model dye. It was found that the degradation efficiency of MnO2 nanorods was a function of initial acid orange II concentration, MnO2 nanorods concentration, and the proton concentration. The apparent reaction orders for the initial acid orange II concentration, MnO2 nanorods concentration and the proton concentration were determined to be −0.76, 0.37 and 0.12, respectively. It was found that the degradation efficiency for 60 ppm acid orange II reached 99% with 0.5 g L−1 MnO2 nanorods concentration at pH 2.0 after 60 min, demonstrating its higher degradation efficiency in aqueous solution. The apparent activation energy of the degradation reaction of acid orange II was calculated to be 17.3 kJ mol−1. Furthermore, MnO2 nanorods were demonstrated to have superior durability during regeneration tests.
Keywords: acid orange II, degradation, hydrothermal methods, MnO2 nanorods