Fe3S4/biochar catalysed heterogeneous Fenton oxidation of organic contaminants: Hydrogen peroxide activation and biochar enhanced reduction of Fe (III) to Fe (II)

Greigite and biochar are two important materials recently gaining importance in Fenton catalysis to remove organic contaminants. Each material, however, has significant drawbacks. For instance, biochar is challenging to remove from reaction media despite having good Fenton activities, whereas greigite (FS) exhibits limited Fenton activities in the absence of light. To make both materials useful, we prepared Fe3S4/biochar (FSBC) composite to enhance the reactivity, stability, and reusability, which could be used for large-scale applications in organic pollutant degradation. At room temperature, the developed catalysts demonstrated good Fenton degradation efficiency toward cationic and anionic dyes as well as phenols. About 90.2 % of Eriochrome Black T (EBT) degradation was accomplished at pH 4 within 1 h without light irradiation. The activation of H2O2 to generate hydroxyl radicals was enhanced by the addition of biochar to the Fe3S4 for the degradation of pollutants. The electrons produced by the biochar and the S-generated specie on the Fe3S4 surface boost the surface iron redox cycle with the regeneration of Fe2+ ions. The biochar has a crucial role in enhancing the activity by 10 % in 1 h in the presence of magnetic Fe3S4 with a rate constant of 0.0372 min(-1).The biochar provides stability to the Fe3S4/biochar composite with minimum Fe leaching and is recovered magnetically from the reaction mixture by using external magnets, which can be used for five catalytic cycles without significant loss of catalytic activity. The reported catalyst, which overcame the individual limitations of both the FS and biochar to improve catalyst activity and magnetic separation, will serve as the foundation for creating novel catalyst systems for the future degradation of organic pollutants.