Activation of peroxymonosulfate by magnetic Fe3S4/biochar composites for the efficient degradation of 2,4,6-trichlorophenol: Synergistic effect and mechanism

The synergistic catalytic degradation of metal carbon-based composites is a feasible strategy to improve the efficiency of advanced oxidation processes (AOPs) by means of green chemistry. In this work, Fe 3 S 4 nanoparticles were anchored on the surface of peanut shell biochar to prepare magnetic Fe 3 S 4 /biochar (Fe 3 S 4 /BC) composites, which were applied to activate peroxymonosulfate (PMS) to degrade 2,4,6-trichlorophenol (2,4,6-TCP). The addition of biochar not only reduced the aggregation of Fe 3 S 4 nanoparticles, but also accelerated the electron transfer rate, and the constructed C-O-Fe bridges accelerated the regeneration of Fe(Ⅱ), which made Fe 3 S 4 /BC have better catalytic performance than pure Fe 3 S 4 even though the use of metal sulfides was reduced. Fe on the surface of Fe 3 S 4 /BC was the catalytic reaction center. The dominant role of sulfate radical (SO 4 ·- ) and hydroxyl radical (HO·) on the degradation of 2,4,6-TCP was verified by electron paramagnetic resonance (EPR) and free radical quenching experiments. The mechanism of C-O-Fe bridges was verified by density functional theory (DFT) calculation. The mechanism of PMS activation by Fe 3 S 4 /BC was elucidated by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Based on the detection results of intermediate products, the possible degradation pathways to 2,4,6-TCP were proposed. This work provides new insights into the synergistic catalytic mechanism of metal carbon-based sulfides and promotes the development of environmentally friendly and efficient metal carbon-based catalysts.