Degradation of azo dye orange G in aqueous solutions by persulfate with ferrous ion

Abstract

The oxidative degradation of azo dye, Orange G (OG), in aqueous solutions by the persulfate/Fe?? reagent has been investigated. Effects of pH, dosages of persulfate and Fe??, temperature, and the presence of inorganic ions (Cl?, NO??, HCO?? and H?PO??) on OG degradation were examined in batch experiments. The OG degradation by the persulfate/Fe?? reagent was found to follow the first-order kinetic model. Under an optimum condition ([persulfate] = 4 mM, [Fe??] = 4 mM and pH 3.5), the OG degradation in aqueous solutions with an initial concentration of 0.1 mM was achieved by 99% within 30 min. The OG degradation increased with an increased dosage of both persulfate and Fe??. The experimental results showed that increasing the reaction temperature from 293 to 313 K was beneficial to the OG degradation, but not as efficient as chemical activation with Fe?? at ambient temperature. In the meantime, the apparent activation energy for the OG degradation was determined to be 92.2 kJ mol??. Furthermore, the results demonstrated that the OG degradation could be significantly inhibited due to the existence of inorganic ions in a sequence of NO?? < Cl? < H?PO?? < HCO??. The experiments also demonstrated that the persulfate/Fe?? reagent can degrade OG in aqueous solutions to a higher degree than the Fenton's reagent, which is beneficial to the mineralization of azo dyes.