Mechanism of iron-activated ozone/persulfate coupled oxidation for petroleum-contaminated soil

Abstract

Soil contamination by petroleum remains a critical environmental challenge. Single oxidation methods, while widely employed for remediation, often exhibit limitations in effectively degrading these contaminants. This hinders their broader application and necessitates the investigation of the complementary effects of commonly employed single oxidation method such as ozone (O3) and persulfate (PS) oxidation to explore their potential for enhanced degradation. In this study, the O3/PS coupling oxidation system activated by iron-loaded activated carbon (Fe@AC) was employed for the remediation of petroleum contaminated soil, and to evaluate the removal efficiency and underlying mechanism for petroleum contaminants. The results demonstrated a significant improvement in the apparent reaction rate constant of the O3/PS/Fe@AC system, recorded at 0.1253 h−1. This rate was approximately twice that of the PS/Fe@AC system (0.0572 h−1) and two orders of magnitude greater than the Fe2+/PS system (0.0014 day−1). Under the conditions of 6 % PS dosage, 0.6 % Fe@AC dosage, a soil-to-water ratio of 1:2, an O3 gas flow rate of 2.5 mg/L, and a pH of 5 at room temperature, the O3/PS/Fe@AC system removed 46.8 % of total petroleum hydrocarbon at an initial concentration of 5000–6000 mg/kg within 3 h. The reaction of the O3/PS/Fe@AC system involved multiple radicals, such as sulfate radicals (SO4•-), hydroxyl radicals (•OH), and superoxide radicals (O2•-), with the reactivity of SO4•- enhanced by O3. This study demonstrates an efficient method for remediating petroleum contaminated soil, providing a theoretical and technical foundation for the application of the O3/PS/Fe@AC system.