Modifying organic carbon in Fe3O4-loaded schwertmannite to improve heterogeneous Fenton activity through accelerating Fe(II) generation

[Display omitted] •Adding Fe3O4 in biogenic schwertmannite growth enhances organic carbon production.•Electrons can be provided by organic carbons for promoting ≡Fe(II) generation.•Fe3O4/Sch/C shows excellent catalytic activity at a wide reaction pH (2–8) range.•The most reactive sites of fluoroquinolone antibiotic are summarized. The conversion of ≡Fe(III) to ≡Fe(II) in the heterogeneous Fenton is low efficient to enhance catalytic activity. Biogenic schwertmannite (Sch), as an iron-based catalyst, is usually formed via Fe(II) oxidation mediated by Acidithiobacillus ferrooxidans (A. ferrooxidans), and contains low organic carbon mainly originated from exopolymeric substances. Owing to the magnetic inter-attraction between A. ferrooxidans and Fe3O4, the introduction of strong magnetic Fe3O4 during synthesis process of biogenic Sch can modify more organic carbon in Sch-based catalyst. Surprisingly, Fe3O4-loaded Sch with organic carbon (Fe3O4/Sch/C) exhibits much higher activity for fluoroquinolone antibiotics degradation than Sch, Fe3O4, and Fe3O4-loaded Sch without organic carbon, which is mainly ascribed to more electrons provided by organic carbons for promoting ≡Fe(II) generation in heterogeneous Fenton. This finding not only provides an ecofriendly, cost-effective, and efficient catalyst, but also gives a new sights into the potential application of iron oxyhydroxysulfate with green carbon-source for contaminants removal.