Remediation of PAH-contaminated soils by magnetite catalyzed Fenton-like oxidation

Abstract

This is the premier study reporting the degradation of polycyclic aromatic hydrocarbons (PAHs) through Fenton-like oxidation catalyzed by magnetite. Kinetic degradation of PAHs was studied at circumneutral pH by treatments: (i) H2O2+soluble FeII (F), (ii) H2O2+magnetite as iron source (FL) and (iii) H2O2 alone without catalyst (HP). Results show that oxidation of a model PAH compound (fluorenone) spiked on sand resulted in its complete removal by FL treatment but degradation did not exceed 20% in HP or F systems. However, in two PAHs polluted soils (sampled from coking plant sites), negligible oxidation of 16 PAHs was observed regardless of the catalyst used: soluble FeII or magnetite. Then organic extract separated from these soils was added to sand and after evaporation of the solvent, oxidation was performed which resulted in more than 90% of PAHs removal by FL as compared to 15% by F or HP systems. These removal extents decreased by a factor of two when the organic extracts were oxidized in the presence of original soil. PAHs degradation extent was improved in soils pre-treated with availability-enhancement agents such as ethanol or cyclodextrin. Degradation was non-selective and no by-products were observed by GC–MS and μFTIR. Treatment efficiency was highly limited by PAHs availability in soils and the soil matrix effect. This study points out the promising efficiency of magnetite for PAHs oxidation at circumneutral pH over soluble FeII in contaminated soils, and has important implications in the remediation of contaminated soils.