Comparison of catalytic activity for treating recalcitrant organic pollutant in heterogeneous Fenton oxidation with iron-impregnated biochar and activated carbon

Iron-impregnated biochar (Fe-BC) was developed through one-step pyrolysis, characterized, and directly compared with Fe-impregnated activated carbon (Fe-AC) for the removal of methylene blue (MB) in a heterogeneous Fenton reaction (HFR). Fe-BC exhibited significantly higher Fe impregnation efficiency than Fe-AC at the same pyrolysis temperature of 600 °C. Analyses via X-ray absorption near-edge spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy revealed that both Fe-BC and Fe-AC contained Fe species such as Fe3O4, FeOOH, and Fe2O3, with Fe-BC having significantly more reduced Fe(II) than Fe-AC. This result is clear evidence that Fe-BC had better catalytic activity for MB than Fe-AC. The removal efficiencies of MB and total organic carbon by Fe-BC and Fe-AC prepared with optimum Fe impregnation concentration (0.25 M Fe) were 98.3 % and 46.3 %, respectively. In particular, Fe-BC removal of MB was predominantly by degradation due to the HFR, while adsorption was dominant in the case of Fe-AC. In particular, Fe-BC (0.25 M Fe impregnation) showed higher MB treatment efficiency (≥ 65.7 %) and stable release of Fe ions (