Degradation of methylene blue in aqueous solution by ozone-based processes

The aim of this study was to compare the efficiency of conventional ozonation and catalytic ozonation (ozone/activated carbon (O3/AC) and ozone/TiO2/activated carbon (O3/TiO2/AC)) in the degradation of methylene blue (MB) component from MB aqueous solution. The removal rates of color and chemical oxygen demand (CODCr) were assessed to screen the most appropriate oxidative process of MB treatment. In this experiment conditions, the color was completely disappeared in the presence of TiO2/AC catalyst, after 40 min of reaction time. However, only ozone system still existed 11.8% MB in aqueous solution, while in case of O3/AC system MB of 4.6% was not removed. In the COD removal experiment, the catalytic ozonation process showed a superior performance, compared to that of the conventional ozonation. COD removal efficiency was significantly promoted in the presence of catalysts such as AC and TiO2. O3/TiO2/AC was found to be the most effective approach to eliminating the color and enhancing COD removal efficiency. The catalyst of TiO2/AC was characterized by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).