A Comparative Study of Ozonation, Homogeneous Catalytic Ozonation, and Photocatalytic Ozonation for C.I. Reactive Red 194 Azo Dye Degradation

In this study, the decolorization, dearomatization, and mineralization efficiencies of different advanced oxidation processes (AOPs; namely O 3 , O 3 /Fe(II), O 3 /Fe(II)/UVA, and O 3 /TiO 2 /UVA) were investigated for the azo dye C.I. Reactive Red 194 (RR194). The effects of pH (3–11), amount of TiO 2 (0.05–1 g/L), and concentration of Fe(II) (0.1–1.6 mM) were investigated for the applied methods. The decolorization and mineralization efficiencies of the photocatalytic ozonation system (O 3 /TiO 2 /UVA) were increased by decreasing the pH of the dye solution in contrast to the ozonation system (O 3 ). Decolorization of RR194 was increased in the photocatalytic ozonation system with an increasing amount of catalyst however, a decreasing was occurred for the homogeneous catalytic system (O 3 /Fe(II)) when increasing the concentration of catalyst. The decolorization efficiency of the homogeneous catalytic system (O 3 /Fe(II)) was enhanced when combined with UVA light. In our study, the most efficient method for dearomatization and mineralization was the O 3 /TiO 2 /UVA among the applied AOPs.