Insights to PFOS elimination with peroxydisulfate activation mediated by boron modified Fe/C catalysts: Enhancing mechanism of boron and PFOS degradation pathway

In this study, the boron-doped iron-carbon composite (Fe@B/C-2) was prepared via a simple solvothermal and secondary calcination process by using iron metal–organic frameworks (Fe-MOFs) as precursor. The obtained Fe@B/C-2 possessed abundant active sites and low iron ion leaching, and exhibited excellent performance on peroxydisulfate (PDS) activation for efficient PFOS (10 mg/L) degradation (94 %) in 60 min, with 0.2 g/L of catalyst dosage, 1.0 g/L of PDS dosage and at 5.0 of initial pH. The radical scavenging and electron paramagnetic resonance (EPR) tests demonstrated that SO₄·⁻ and ·OH were the primary active species during PFOS elimination. Under the attack of these species, PFOS was first transformed into PFOA, followed by a sequential defluorination process, and lastly mineralized into CO₂ and F⁻. Notably, DFT results revealed that Fe species, -BC₃/-BC₂O structures on the carbon matrix performed crucial roles in PDS activation. The extraordinary catalytic activity of Fe@B/C-2 was attributable to the synergistic effects of Fe nanoparticles and the B-doped on carbon matrix. The doped B not only could activate the inert carbon skeleton and provided more catalytic centers, but also could accelerate the electron transfer efficiency, leading to a boost in PDS decomposition.