Synergistic Fe-Mn co-doped biochar for enhanced periodate activation: unveiling dual-radical and non-radical pathways in oxytetracycline degradation

The contamination of wastewater by antibiotics poses significant ecological risks. Here, a novel Fe-Mn co-doped nitrogen-doped biochar (Fe-Mn@NBC) was synthesized from corn straw via impregnation-chelation-pyrolysis to activate periodate (PI) for oxytetracycline (OTC) degradation. The Fe-Mn@NBC/PI system demonstrated outstanding degradation performance, achieving an OTC removal rate of 96.2% within 90 min, with a reaction constant of 0.237 min-1. The unit degradation efficiency of OTC for Fe-Mn@NBC/PI system was calculated to be 320.7 mg·(g·mmol)−1, outperforming many similar catalysts reported in the literature. This enhanced performance is attributed to the porous structure, large surface area, and abundant active sites of Fe-Mn@NBC, which optimize charge distribution and facilitate electron transfer. The system maintained good degradability and reusability under various hydraulic conditions (pH, inorganic anions, humic acid, actual water). Mechanistic studies revealed that 1O2, O2•−, and IO3• were the dominant reactive species. Using HPLC-MS and Fukui function analysis, electron-rich groups (-CONH2, -COOH) were identified as primary attack sites, leading to three proposed OTC degradation pathways, with key intermediates showing low toxicity via T.E.S.T. analysis. This study not only presents a sustainable approach for repurposing waste corn stalk biomass but also offers a cost-effective and eco-friendly solution to combat antibiotic pollution in wastewater.