Paper Title
SYNTHESIS OF BA-DOPEDα -MNO2NANOWIRES AND EVALUATION OF THEIR CATALYTIC ACTIVITY ON DEGRADATION OF ORGANIC DYES

Abstract
Abstract - Pollution of environment and particularly pollution of water and air by organic compounds causes many health problems, hence the need to find suitable and effective solutions to fight against environmental pollution and preserve the life of humans, animals and plants. The degradation of pollutants by the oxidation/reduction reaction is a promising alternative.The aim of this work is to develop a sufficiently efficient catalyst.In this perspective, Ba-doped α-MnO2 nanowires with different concentrations of Ba have been synthesized using a simple hydrothermal process, to be used as catalysts in the degradation of organic pollutants such as methylene blue dye. KMnO4, MnSO4.H2O and BaCl2 were used as chemical reagents. The Sr-doping concentrations were 0, 2, 4, 6, and 8 wt%. After stirring and heating at 50°C for one hour, a homogeneous solutionwasobtained which was transferred into a stainless-steel autoclave (capacity 160 ml). The autoclave was heated to 90°Cduring 24hours and then allowed to cool down to room temperature naturally. The obtained brown nanopowders have been systematically characterized by X-ray diffraction, UV-Visible absorption spectroscopy, and scanning electron miscroscopy (SEM). The results demonstrate that the synthesized materials correspond to the manganese oxide α-MnO2 phase which has the symmetry of thetetragonalspace group I4/m. The SEM microscopy revealed-MnO2 crystallites with nanowire morphology whichhave length up to 5µm and nanometric cross section. The Ba-doped α-MnO2 samples depict a weak absorption in the visible range and have optical band gap energies lower than that of undoped α-MnO2.The efficiency of catalytic and photocatalytic activity of the synthesized samples was tested on the degradation of the Methylene blue (MB) organic dye. It was found that the α-MnO2 nanowires have a large catalytic and photocatalytic activity. Moreover, the Ba-doped α-MnO2samples have enhanced the photodegradation of the Methylene blue under solar irradiation and the degradation rate has reached more than 98%, improving widely the photocatalytic activity. Keywords: Hydrothermal Synthesis, Ba-dopedα-MnO2 nanowires, Catalytic and Photocatalytic Activity, Methylene Blue Dye.