Pyrene contaminated soil remediation using microwave/magnetite activated persulfate oxidation

Polycyclic aromatic hydrocarbons (PAHs) are important mutagen prevalent in the contaminated sites, bringing potential risks to human health. Iron oxides are important natural components in soils. Pyrene removal in soil using persulfate (PS) oxidation activated by microwave (MW) and magnetite (Fe₃O₄) was investigated. Fe₃O₄ significantly promoted pyrene removal in the soil; 91.7 % of pyrene was degraded within 45 min treatment. Pyrene removal rate in the Fe₃O₄/MW/PS system was 5.18 and 3.00 times higher than that in the Fe₃O₄/PS and MW/PS systems. Increasing in Fe₃O₄ dosage, PS concentration, MW temperature, and soil moisture content in the selected range were conducive for pyrene degradation. SO₄^•-, ^•OH, O₂^•-, and ¹O₂ were responsible for pyrene degradation, and the conversion of Fe (Ⅱ) in the Fe₃O₄ to Fe (Ⅲ) contributed to the formation of O₂^•- and ¹O₂. Characteristic bands of pyrene were more obviously destroyed by the Fe₃O₄/MW/PS oxidation, in comparison with MW/PS oxidation. Ring hydroxylation and ring-opening reactions were the main degradation pathways of pyrene. The toxicities of the formed byproducts were significantly reduced after treatment. This study provided a promising option for pyrene contaminated soil remediation.