Photocatalytic performance of TiO2 particles in degradation of various organic dyes under visible and UV light irradiation

Abstract

Various types of organic dyes are discharged by textile/batik industry daily. These are the problematic issues for water treatment system based on semiconductor photocatalysts as various types of organic dyes could degrade differently due to different in molecular nature. In this study, the photocatalytic activity of TiO2 particles in degradation of various types of organic dyes, i.e. methylene blue (MB), rhodamine B (RhB) and bromocresol green (BG) dyes, under visible light and UV light irradiation were systematically studied. The crystal structure and morphology of TiO2 particles were analyzed by X-ray Diffraction Spectroscopy and Field-emission Scanning Electron Microscope, respectively. The average diameter of Rutile-TiO2 was 92 ± 39 nm. The degradation of organic dyes was monitored from its maximum absorption peak measured by ultra violet-visible spectrophotometer. Under UV light irradiation, high degradation efficiencies of dyes were observed and followed the order of: RhB > MB > BG, indicating that the dyes were mineralized by photogenerated hydroxyl free radicals and/or superoxide free radicals. Under visible light irradiation, the photodegradation efficiencies followed the order of: MB > RhB > BG. As compared to UV light, the degradation of organic dyes were different in visible light which relied on the electrons ejected from dye molecules upon absorbing light energy.