Efficient oxidative remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soil: A thorough comprehension of Fe-loaded biochar activated persulfate

The porous and defective structure of biochar (BC) can accelerate surface electron transfer, promote the generation of more reactive oxygen species (ROS) by persulfate (PS), and effectively degrade organic pollutants in the soil. Electron transfer is a crucial link in this process, directly determining its oxidative degradation efficiency. In this study, using a novel strategy of enhancing electron transfer on the surface of BC by loading iron, three Fe-loaded BC activators (Fe-FeO_x@BC, Fe₂O₃@BC and Fe₃O₄@BC) were synthesized to support the oxidative remediation of benzo(a)pyrene (BaP, Model compound of PAHs)-contaminated soil by PS. The results showed that Fe₃O₄@BC supported PS oxidation and remediation of BaP-contaminated soil had the best effect among the three BC-based activators, and the reuse effect was stable. Under the conditions of Fe₃O₄@BC addition of 1.00 wt%, PS addition of 0.75 wt%, reaction temperature of 35 °C, and solid-liquid ratio of 1:2.5, the removal rate of BaP in the soil reached the maximum of 93.84% at 120 min, and the soil toxicity was significantly reduced after remediation. The defect structure, conductive magnetic particles, and active functional groups on the surface of Fe₃O₄@BC were the key factors for activating PS to degrade BaP. With the combined action of the free radical pathway caused by ROS and the non-free radical pathway caused by ¹O₂, electron transfer, and active functional groups, BaP was degraded to small molecules such as CO₂ and H₂O, achieving rapid and efficient remediation of organic contaminated soil.