Mechanistic insights into removal of norfloxacin from water using different natural iron ore - biochar composites: more rich free radicals derived from natural pyrite-biochar composites than hematite-biochar composites

Two novel magnetic hematite-biochar composites (FOC) and pyrite-biochar composites (FSC) were successfully fabricated through co-pyrolysis as low-cost materials to remove norfloxacin (NOR) from aqueous solution. Multiple characterization results revealed that natural hematite and natural pyrite were successfully loaded on the surface of biochars respectively. After introducing Fe and S, the removal performance of FSC was better than that of FOC and primitive biochar (BC). This was not only due to the increase of the average pore width and abundant surface functional groups, but also since that (OH)-O-center dot and SO4 center dot - played the key role in the removal of NOR, which was confirmed by Election Paramagnetic Resonance (EPR) experiments. High Resolution Mass Spectrometer (HRMS) was used to determine the transformation intermediates of NOR and the possible degradation pathways were proposed. Excellent adsorption performance and free radicals ((OH)-O-center dot and SO4(center dot -)) action made FSC had the best removal performance on NOR in this study.