Degradation of fluoranthene in aqueous solution and soil media by citric acid-enhanced FeS catalyzed sodium percarbonate

Mackinawite (FeS) is a promising catalyst for advanced oxidation processes (AOPs), but its role in activating sodium percarbonate (SPC)-dominated oxidation remains unclear. Herein, citric acid (CA) was introduced as a synergistic agent to enhance FeS activation of SPC, demonstrating that SPC/FeS and SPC/CA systems hardly removed 6.8 % and 7.6 % of fluoranthene (FLT), respectively, while SPC/FeS/CA process achieved a significant 96.2 % FLT degradation. Reactive oxygen species (ROS) analysis identified HO and O 2 − as the dominant contributors to FLT degradation. X-ray photoelectron spectroscopy (XPS) confirmed that S(-II) facilitated the Fe(III)/Fe(II) redox cycle, ensuring prolonged FLT degradation, which was further confirmed through Na 2 S experiments. GC–MS identified benzoic acid (BA) and phthalic acid (PA) as degradation intermediates with reduced toxicity than FLT, highlighting the environmental safety of the proposed technique. SPC/FeS/CA system effectively mitigated the inhibitory effects of neutral to weakly alkaline pH conditions (8.0–10.0) and achieved significant FLT degradation (60.7 %) even at pH 11.0. In soil slurry experiments, the process removed 80 % of FLT within 12 h. The system effectively degraded other polycyclic aromatic hydrocarbons (PAHs), including naphthalene and phenanthrene, demonstrating its broad applicability for remediating PAHs-contaminated environments. This study introduces a novel SPC-dominated AOP strategy, leveraging FeS as a robust catalyst, and offers valuable insights for advancing efficient PAHs remediation technologies.