Preparation and application of red mud-based zero-valent iron heterogeneous Fenton catalyst: A new idea for red mud recycling

As an abundant hazardous waste, red mud needs a simple and effective mean of resource utilization. Herein, a novel zero-valent iron heterogeneous Fenton catalyst RMB-900 was synthesized by pyrolysis (900 °C) using red mud and straw with a facile solvent-free carbothermal redox approach. X-ray diffraction analysis showed that Fe₂O₃ in the red mud was reduced to Fe⁰. Characterization data showed that RMB-900 was a zero-valent iron loaded porous material. Under the conditions of 2.86 mM H₂O₂, 100 mg/L acid red G, and 1 g/L RMB-900, 98% of acid red G was removed within 10 min, the reaction rate constant is 6.7 folds higher than that of commercial zero-valent iron. The RMB-900/H₂O₂ system also showed good degradability to antibiotics (Sulfamethoxazole, Ibuprofen and Carbamazepine). H₂O₂ is mainly catalysed by Fe⁰ in RMB-900 to generate •OH for ARG degradation. RMB-900 still showed excellent catalytic performance after standing for four months and after being reused nine times. This study not only prepared a catalyst with low cost, high stability, and great potential for wastewater treatment through a simple and green solvent-free method, but also provided a research basis for further exploration of red mud-based catalysts.