Abstract: Red mud is an alkaline solid waste produced during aluminum production，and can be recycled by converting acidified red mud into Fenton-like catalyst. In this study, red mud was acidified using hydrochloric acid and then loaded on cobalt oxides via impregnation method to prepare a heterogeneous catalyst. Peroxymonosulfate (PMS) was activated by the as-prepared catalyst to remove Rhodamine B. The effects of catalyst dosage, PMS concentration, initial Rhodamine B concentration, and reaction temperature on the removal efficiency were investigated. Results show that the removal efficiency of Rhodamine B was 95.9% at the catalyst dosage of 0.05 g/L, PMS concentration of 0.1 mmol/L, initial solution pH of 4.8, temperature of 65℃, Rhodamine B concentration of 10 mg/L, and reaction time of 50 min. Free radical scavenging experiment confirmed the presence of SO₄^-· ,·OH, and singlet oxygen (¹O₂)in the reaction system, where ¹O₂played a major role in the oxidation of Rhodamine B. Even in the third reuse of the catalyst, the removal efficiency of Rhodamine B remained above 80%.

Key words: red mud, cobalt oxides, peroxymonosulfate, Rhodamine B, singlet oxygen