Magnetic biochar derived from Eichhornia crassipes for highly efficient Fenton-like degradation of antibiotics: Mechanism and contributions

The active components in biochar decrease markedly after hydrogen peroxide activation and the recycle of exhausted biochar is inconvenient, which hinder the application of biochar in advanced oxidation processes . In this study, magnetic biochar was successfully prepared using Eichhornia crassipes and iron salts via the impregnation-pyrolysis method. The efficiency of metronidazole degradation was 97.4% in the magnetic biochar/hydrogen peroxide system, which was approximately 28 times higher than that in the biochar/hydrogen peroxide system. Free radical quenching experiments and electron paramagnetic resonance analyses demonstrated that metronidazole elimination in the magnetic biochar/hydrogen peroxide system was mainly attributable to hydroxyl radicals , and the contribution of hydroxyl radicals to metronidazole degradation was calculated to be approximately 84.0%. Hydrogen peroxide activation by persistent free radicals and functional groups in the magnetic biochar during metronidazole degradation was negligible. Moreover, Fe(II) in the magnetic biochar was found to play the key role in hydrogen peroxide activation, with its contribution to metronidazole degradation accounting for nearly 90.0%. This work provides a new method to utilize harvested E. crassipes to generate high-performance magnetic biochar that can be used for efficient elimination of antibiotics from aquatic environments.