Photocatalytic Degradation of Methylene Blue Dye Using Zinc Oxide Nanoparticles under Solar Irradiation

Abstract

The discharge of synthetic dyes from textile and other industries colours water bodies and resists conventional treatment, and heterogeneous photocatalysis using semiconductor nanoparticles offers a means of degrading such dyes into harmless products using light. This paper reports the photocatalytic degradation of methylene blue dye using zinc oxide nanoparticles under solar irradiation. The degradation was studied as a function of irradiation time, with and without the catalyst, and the effects of the catalyst dose were examined, while the reaction kinetics were analysed. The results show that the dye was degraded efficiently in the presence of the zinc oxide catalyst under sunlight, with the degradation far exceeding that by photolysis alone, that the degradation increased with catalyst dose up to an optimum beyond which it declined slightly, and that the degradation followed pseudo-first-order kinetics. The study demonstrates that zinc oxide nanoparticles are an effective photocatalyst for the solar degradation of methylene blue and discusses the factors governing the process.  KEYWORDS: Photocatalysis, Methylene Blue, Zinc Oxide, Dye Degradation,Solar Irradiation, Water Treatment, Reaction Kinetics