PHOTOCATYLITIC DEGRADATION OF METHELENE BLUE DYE USING ZnO NANORODS AND SUN LIGHT.

Abstract

The ZnO nanorods have been successfully synthesized by seed layer preparation using dip coating method and by growth layer preparation using hydrothermal method. The prepared ZnO nanorods were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and UV-Visible spectrophotometer (UV-Abs).. These ZnO nanostructures were explored as catalyst for solar-light induced photo catalytic degradation of methylene blue dye in an aqueous solution. The degradation rates depend on the dye structure, concentration, solvent-dependent ZnO film morphologies, pH of the medium and excitation light source. The photocatalytic performances of the obtained ZnO nanorods were deeply investigated for possible application of textile/water treatment. …………………………………………………………………………………………………….... Introduction:-The ZnO have been widely used metal oxide semiconductor material for photo catalysts processes. The ZnO have a band gap of about 3.38 eV and high exciton binding energy of 60 meV.[1] The synthesis of ZnO nano particles with different morphologies and sizes were made by researches. One-dimensional nanostructures (e.g., nano wires, nanorods, nano needles, nano tubes, columns and helices) play an important role in many applications because they possess high surface to volume ratio with short diffusion length area.[2-5].The one-dimensional nanostructures have large junction area which imparts low reflectance provide a direct pathway for charge transport [6].Also, these materials reduce the recombination of excitons and thus show high energy conversion efficiency and since ZnO has a wide band gap, its use is restricted to the visible region.The photo catalytic activity of the investigated materials was tested by the degradation experiments, the samples were irradiated by solar light for 120 minutes in order to remove the hydrocarbons from the sample surface.. The glass substrates were dipped in methelene blue aqueous solutions where samples are immersed was irradiated by a solar light. The irradiated solution was measured at regular time intervals with an UV Vis spectrophotometer JASCO-570 UV-Vis spectrophotometer. Degradation of methelene blue was evaluated by the absorption peak at 655nm. The photo degradation reaction was calculated from the linear plot of ln [Co/C] versus from the irradiation time. The decomposition of the methelene blue in the absence of any photo catalyst materials was checked as a reference. [7][8]