Improving heterogeneous Fenton reactivity of schwertmannite by increasing organic carbon and its promising application

Iron-based heterogeneous Fenton is a promising economic and eco-friendly technology in the degradation of organic pollutants, but the low conversion of ≡Fe³⁺ to ≡Fe²⁺ causes the low catalytic activity. Schwertmannite (Sch) formed via Fe(II) oxidation mediated by Acidithiobacillus ferrooxidans (A. ferrooxidans), resulting in the existence of low organic carbon (mainly from A. ferrooxidans cells) in Sch. Owing to magnetic inter-attraction between magnetosome-containing A. ferrooxidans and Fe₃O₄, A. ferrooxidans as organic carbon (OC) modified Fe₃O₄/Sch (namely Fe₃O₄/Sch/OC) was obtained by the introduction of Fe₃O₄ into synthetic process of Sch. Fe₃O₄/Sch/OC exhibited higher degradation efficiency (>95%) of antibiotics than Sch, Fe₃O₄ and Fe₃O₄/Sch, which was mainly ascribed to OC as electron donor and electron-transfer mediator for promoting ≡Fe²⁺ regeneration. Moreover, in situ H₂O₂ could be generated at a wide initial pH (3–9) via Fe₃O₄/Sch/OC-driven oxygen reduction reaction, and H₂O₂ was immediately activated to produce •OH for degrading organic pollutants (e.g., dyes, antibiotics). Considering the excellent arsenic (As) adsorption performance of Sch and the property of Fe₃O₄/Sch/OC to produce in situ H₂O₂, Fe₃O₄/Sch/OC-catalyzed in situ-generated H₂O₂ will be a promising strategy to synchronously remove antibiotics and As from livestock and poultry breeding wastewater.