Enhanced Catalytic Degradation of Acid Orange 7 Dye by Peroxymonosulfate on Co3O4 Promoted by Bi2O3

Abstract

In this study, Bi₂O₃-Co₃O₄ composite oxides were prepared and their catalytic efficiency to activate peroxymonosulfate (PMS) towards the degradation of Acid Orange 7 dye (AO7) was evaluated. The characterization of the synthesized catalysts was carried out by XRD, TEM, XPS, FT-IR, and ICP-OES analyses. The increased basicity of the Bi₂O₃-Co₃O₄ hybrids contributed to the much better catalytic activity in PMS activation resulting in a considerably higher rate of AO7 degradation compared to that obtained with bare Co₃O₄. The sample with 50 wt.% Bi₂O₃ showed the best performance under a broad pH range with very low Co leaching of 72 mg/L even under acidic conditions. Degradation of 50 mg/L AO7 reached almost 100% within a short duration of 12 min by using very low catalysts concentration of 0.1 g/L and [PMS]/[AO7] = 6. The influence of the Bi₂O₃ content, catalyst dosage, molar ratio of [PMS]/[AO7], initial pH, and temperature on AO7 degradation were studied. Surface-bound sulfate radicals generated in the Bi₂O₃-Co₃O₄/PMS oxidation system were proved as the predominant radical species through radical quenching experiments.