Catalytic degradation of crude oil residues extracted from contaminated soil by heterogeneous Fenton process using natural magnetite

Abstract The presence of toxic compounds to humans in crude oil requires the purification of contaminated environment. In this study, physicochemical characterization of paraffinic petroleum residue extracted from contaminated soil, revealed the presence of benzene, toluene, 3-methylphenanthrene, and methylphenanthrene. Crude oil residues were degraded by heterogeneous Fenton process using cheap material (natural magnetite from Mount Ofoud) as heterogeneous catalyst. This magnetite, not yet upgraded, had a specific surface area of 69.742 m2/g and an average pore diameter of 2.8 nm according to the BET analysis. XRF analysis of pretreated material also indicates that iron was dominant at 97.09% (with 77.03% Fe3O4 generated by XRD), while the minor elements are Ti, Mg, Ni, Co and Mn. Using heterogeneous Fenton oxidation process at room temperature, the residual COT concentrations could be optimally diminished by up to 77–78% by applying H2O2/Fe3O4 molar ratio of 5 and pH of 6.5 in the investigated range of 1000 mg COT/L. The oxidation reactions lasted 48 hours. Chromatographic analysis shows that the degradation rate of alkanes with carbon atoms greater than 15 is low. The results of this study show that magnetite is effective at sub-neutral pH and H2SO4 is more appropriate than HCl for pH adjusting.