Abstract: In this study, cobalt was loaded on 2-methylimidazole-modified Mg-Al layered double hydroxide (LDH-MI) to synthesize Co/LDH-MI catalyst, which was employed to activate hydrogen peroxide for the degradation of tetracycline (TC) in aqueous solution. The microstructure, elemental distribution and chemical state of Co/LDH-MI were characterized systematically. The effects of catalyst dosage, solution pH and coexisting interfering ions on catalytic performance were investigated, and the corresponding degradation mechanism was also explored.The results demonstrated that 2-methylimidazole modification obviously increased the surface hydroxyl groups of LDH, which provided sufficient anchoring sites for cobalt species. The cobalt loading capacity of modified Co/LDH-MI was 2.8 times higher than that of unmodified Mg-Al LDH, which enriched catalytic active centers and greatly improved catalytic activity. Under the conditions of a catalyst dosage of 200 mg/L,an initial pH of 5 and a temperature of 25 °C, the removal efficiency of TC reached 98.7% within 10 min. Its pseudo-first-order kinetic constant was 3.02 times that on the unmodified catalyst. After four recycling experiments, the TC removal rate remained above 89%. Electron paramagnetic resonance and radical quenching experiments verified that hydroxyl radical (·OH) was the predominant reactive oxygen species in this system.

Key words: Mg-Al layered double hydroxide, cobalt, Fenton-like reaction, tetracycline