Purpose <p>Increasing attention has been paid to the heterogeneously activated persulfate (PS)-based advanced oxidation technologies (AOTs) in contaminated soil remediation. However, PS activation by ferrous iron (Fe(II))-modified biochar has rarely been explored.</p> Materials and methods <p>This study has been fabricated by loading Fe(Ⅱ) into biochar to activate PS for polycyclic aromatic hydrocarbons (PAHs) remediation. Pyrolysis temperature of biochar, dosages of PS/biochar, water-soil ratios were studied to evaluate the performance of PS activation by Fe-BC400 and Fe-BC800 to degrade anthracene (Ant) and phenanthrene (Phe) in soil.</p> Results and discussion <p>Fe-BC800 exhibits superior PS activation efficiency due to its dense carbon structure and more active sites, which consequently enhanced removal of anthracene and phenanthrene by 60%. When the PS-to-iron-modified biochar molar ratio is 5:1 and water-soil ratio is 2:1, the optimal removal efficiency and cost-effectiveness are achieved, with the removal rates of Ant and Phe reaching 92% and 80%, respectively. Besides, the addition of sodium dodecylbenzene sulfonate (SDS) effectively promoted the degradation of both anthracene and phenanthrene. Further analyses confirmed PAHs into less toxic intermediates through radicals of sulfate radical (SO₄^•−), hydroxyl radical(^•OH) and Singlet Oxygen (1O₂) generated from persulfate activation process, with SO4^•− contributing dominantly to pollutant degradation.</p> Conclusions <p>The results of this study provide a new PS activation strategy using Fe-modified biochar that will contribute to rapid degradation of organic contaminants in site soils using PS-based AOTs.</p> Graphical Abstract <p></p>