Unveiling the comparative degradation of fluoranthene by zero-valent iron and sulfidated zero-valent iron nanoparticles activated peroxymonosulfate: Performance and mechanisms

The efficient and eco-friendly remediation of polycyclic aromatic hydrocarbons (PAHs) in soil and groundwater through advanced oxidation remains a critical challenge. In this study, nano zero-valent iron (nZVI) and sulfurized nano zero-valent iron (S-nZVI) were utilized to activate peroxymonosulfate (PMS), demonstrating significant potential for fluoranthene (FLT) degradation. PMS/S-nZVI system outperformed PMS/nZVI system, achieving higher efficiency with lower reagent dosages. Dissolved Fe(II) analysis indicated enhanced Fe(III)/Fe(II) cycling in PMS/S-nZVI system, driven by the synergistic role of elemental sulfur. Both systems generated reactive species (SO 4 − •, O 2 − •, and HO•), with SO 4 − • identified as the dominant contributor to FLT degradation. Water quality variations significantly impacted FLT removal, with PMS/S-nZVI system exhibiting greater adaptability to diverse conditions compared to PMS/nZVI system. FLT degradation was more effective under acidic conditions. The high concentrations of HCO 3 − , Br − , and HA, and the presence of surfactants such as Tween-80 significantly hindered degradation. In contrast, low concentrations of Cl − and HA enhanced the process. Simulated real groundwater experiments revealed that pre-conditioning the solution pH to 5.0 achieved FLT removal efficiencies of 89.9 % and 91.8 % for PMS/nZVI and PMS/S-nZVI systems, respectively, with oxidant dosages increased by fivefold. In water-soil coupled slurry experiments, a water-soil ratio of 15:1, a reaction time of 6 h, and neutral post-reaction pH resulted in FLT degradation exceeding 90 %. This study highlights the potential of PMS-based advanced oxidation processes, particularly PMS/S-nZVI system, as an effective and adaptable approach for the remediation of PAHs-contaminated soil and groundwater.