Oxidative Degradation of Benzo[a]pyrene in Waste Sulfonated Drilling Mud by Iron Activated Persulfate

Abstract

In the oil and gas industry, sulfonated drilling fluid, as a water-based drilling fluid, is applied on a large scale. The waste fluid mixed with drilling cuttings forms solid waste-sulfonated drilling waste (SW-SDM). Considering the water-soluble refractory organic matter in SW-SDM and the possible leaching of soil organic matter, processing SW-SDM to protect soil and groundwater from pollution is urgent. The present article systematically investigated the degradation of benzo[a]pyrene (BaP) in SW-SDM by iron (Fe) activated persulfate (PS) oxidation with special attention to revealing the influence of background Fe on degradation. The experimental results demonstrated that BaP in SW-SDM could be partly degraded by the activated PS oxidation system. Parameters such as the pH and dosages of PS and Fe may greatly influence the experimental results. A higher dosage of Fe inhibits degradation, whereas the addition of a small amount of Fe or even no Fe may facilitate the degradation of BaP. Naturally present Fe(II), Fe(III), and dissolved Fe from SW-SDM itself may activate PS for BaP degradation. The feasibility of the SW-SDM treatment was evaluated. Finally, the degradation intermediates of BaP by Fe and PS oxidation in soil were enriched by solid phase extraction and identified by gas chromatography-mass spectrometry to propose a transformed pathway.