Study on degradation of acid orange II in aqueous solution using one-dimensional MnO2 nanorods

Abstract

MnO(2) nanorods were prepared by the reaction of KMnO(4) and MnSO(4) 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 MnO(2) possessed alpha- and gamma structure. SEM observations showed that the obtained MnO(2) powder possessed a well-defined one-dimensional nanorod-like shape 100 nm wide and 700 nm long. The surface area of the MnO(2) nanorods was 92 m(2) g(-1). The degradation efficiency of MnO(2) 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 MnO(2) nanorods was a function of initial acid orange II concentration, MnO(2) nanorods concentration, and the proton concentration. The apparent reaction orders for the initial acid orange II concentration, MnO(2) 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) MnO(2) 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, MnO(2) nanorods were demonstrated to have superior durability during regeneration tests.