Degradation of Acid Orange 7 by peroxomonosulfate activated with Fe-MnOx

Bimetallic Fe-Mn oxide (Fe-MnOx) was prepared using the sol-gel method to take advantage of the ability of Fe and Mn ions to activate peroxymonosulfate (PMS) in a homogeneous system and avoid pollution caused by metal ions. The degradation process and mechanism were investigated for the removal of Acid Orange 7 (AO7) by using Fe-MnOxas a catalyst to generate powerful radicals from PMS. The effects of ρ(Fe-MnOx), ρ(PMS)0and ρ(AO7)0on the degradation of AO7 were tested. The results showed that with the ρ(Fe-MnOx) from 50 mg/L to 200 mg/L, the degradation rate of AO7 increased from 53.74% to 96.65% at 35 min. However, no significant change in the degradation rate was observed with further increases of ρ(Fe-MnOx). In addition, the degradation rate of AO7 decreased when ρ(AO7)0increased. The reaction of the Fe-MnOxcatalyst-activated PMS was conducted with the addition of one of two probe compounds to detect the generation of reactive oxygen species: ethylalcohol (EA) and tertbutylalcohol (TBA). The degradation rate of AO7 at 55 min was 79.40% by adding EA and 91.33% by adding TBA. Therefore, the oxygen species in the system were identified as mostly sulfate radicals and a small amount of hydroxyl radicals. The results of XRD and XPS indicated that the Fe-MnOxcatalyst consisted of Fe2O3, Mn3O4and Mn5O8, in which the relative molar quantities of Fe3+, Mn2+, Mn4+, O2+and surface hydroxyl oxygen were 20.49%, 26.46%, 5.60%, 32.51% and 14.91%, respectively. The study indicated that Fe-MnOxcatalyst had a low metallic ion leaching, and good ability to activate PMS and degrade organic pollutants into radicals. © 2015, Editorial Board, Research of Environmental Sciences. All right reserved.