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-FeOx@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. © 2024 Elsevier Ltd