Upcycling Red Mud into a Stable Electro-Fenton Catalyst via Ingenious Sn Doping for Efficient Antibiotic Wastewater Treatment

The limited stability of catalysts and their high operational costs present significant challenges to the widespread application of heterogeneous electro-Fenton (HEF) in practical water treatment. Herein, we developed a scalable production (∼1 kg) of a Sn-doped red mud (RM-Sn1.5) catalyst via a straightforward methodology for the HEF system aimed at antibiotic wastewater purification. The RM-Sn1.5 catalyst could remove over 90% of nine antibiotics and two phenolic compounds from water within 90 min, with an electrical energy consumption of 7.37 kWh·m –3 per order. The incorporation of Sn induced the formation of intrinsic oxygen vacancies, which act as electron donors, significantly enhancing the internal electron transfer between Sn and Fe, thereby ensuring sustainable iron cycling to generate hydroxyl radicals. Importantly, the RM-Sn1.5 catalyst demonstrated outstanding catalytic performance, even after 30 cycles of reuse and 6 months of placement. During the treatment of actual pharmaceutical wastewater, 54.5% of COD removal was achieved in just 90 min. This study provides a novel approach to converting industrial waste into a low-cost, sustainable catalyst for the economic treatment of practical wastewater.