Trend in azo dye reactive red 120 degradation by ozonation and advanced oxidation process

Abstract

In this study, the trend of azo dye degradation by ozonation and advanced oxidation process was evaluated base on colour and COD removal efficiency of Reactive Red 120. In addition, FT-IR spectrum was analysed to determine the mechanism of azo dye degradation. Reactive Red 120 has been selected amongst azo dyes due to its high solubility in aquatic environment. Ozone (O3) and ozone combined with hydrogen peroxide (H2O2/O3) were effective for colour removal of azo dye, which imply that both processes tend to oxidize N=N double bond in azo dye. In addition, COD removal is less effective than colour removal, which was proved that O3 and H2O2/O3 treatment tend to degrade azo dye to certain by-product rather than completely mineralize to CO2 and H2O. Higher COD removal observed after O3 treatment in comparison to H2O2/O3 treatment can be explained by the presence of H2O2 in O3/ H2O2 process that leading to the overestimation of COD measurements. FTIR analysis showed there was the greater intensity of the presence of carboxylic compounds for H2O2/O3 treatment compared to O3 treatment.