Reinforced PAHs degradation in industrial site soil by Fe(III)/NaClO catalytic oxidation system: Insights from promoting hydroxyl radicals generation

Great attention has been paid to the removal of polycyclic aromatic hydrocarbons (PAHs) from polluted soil worldwide, because the refractory PAHs have severe carcinogenic, teratogenic, and mutagenic effects that put substantial threats to ecosystem safety and human health. In this study, a Fe(III)/NaClO catalytic oxidation system was employed to achieve an enhanced remediation of PAHs-contaminated industrial site soil. With an optimal mass ratio of Fe(III)/NaClO at 1/6, the removal efficiency of PAHs was improved by 19.6% and 14.8% after 2 and 48 h of reaction compared with using NaClO alone when the concentration of NaClO was set as 2000 mg/L. The degradation behavior of PAHs by Fe(III)/NaClO catalytic oxidation system was investigated in detail. The influence of Fe(III) dosage, NaClO concentration and pH value on PAHs removal was evaluated in-depth. The degradation products were confirmed and degradation pathways were proposed. Generated hydroxyl radicals (•OH) were identified by quenching experiments and electron paramagnetic resonance (EPR) technology, which played synergetic effects in the degradation of PAHs with HClO molecule. Finally, results of phytotoxicity tests demonstrated that the inhibition effects on plants growth decreased obviously of remediated soil. This work provided a catalytic oxidation method with cost-effectiveness, high efficiency and wide applicability for PAHs degradation in industrial site soil.