Photocatalytic decomposition of methyl orange Azo Dye using nanostructured TiO2 photocatalyst

Abstract

An azo compound is an important class of synthetic dyes and is characterized by the presence of one or more azo group (-N-N-) linked between aromatic rings. The release of this coloring agent definitely causes wastewater problems. Photocatalysis is an efficient technique to remove dye pollutants because of several advantages: (a) it produces less harmful end products; (b) non-toxic materials can be used as a semiconductor photocatalyst, such as titanium dioxide (TiO2, and, (c) it can be operated at ambient temperature and atmospheric pressure. In this study, several operational parameters affecting the decolorization and degradation of methyl orange (monoazo dye) - namely the type of TiO2, photocatalyst, calcination temperature of the photocatalyst, photocatalyst dosage, initial dye concentration, H2O2, (oxidant) concentration, initial solution pH, and Pt loading content - were investigated. The experimental results showed that a mesoporous-assembled TiO2; nanocrystal synthesized by a sol-gel process with the aid of a structure directing surfactant and calcined al 500°C provided much better decolorization and degradation performance than various non-mesoporous-assembled commercial TiO2.The optimum conditions were obtained at a photocatalyst dosage of 7g/l, an initial pH of 4.7, exhibiting the highest decolorization rate constant of 1.97 h-1. However, when an optimum Pt content of 0.6 wt.% was loaded on the mesoporous- assembled TiO2 prepare by a single-step sol-gel method and calcined at 500°c, the decolorization rate constant was enhanced to 2.16 h-1