Beneficial utilization of ball-milled carbon sand to activate peroxymonosulfate oxidation: Quantitation of ROS using probe-based kinetic models and mechanism insights

In this study, the oil sand was treated with an integrated process of pyrolysis and ball milling, and the obtained ball-milled carbon sand (BMCS) was utilized as peroxymonosulfate (PMS) activator to treat wastewater containing aniline (AN). Quenching experiments and electron paramagnetic resonance (EPR) confirmed the existence of sulfate radical (SO4 center dot-), hydroxyl radical (<middle dot>OH) and singlet oxygen (O-1(2)) in the BMCS/PMS system. A probe-based kinetic model was constructed to describe the degradation process of pollutants in the BMCS/PMS system, quantified the exposure of each reactive oxygen species and their contributions to AN degradation. BMCS activated PMS to quickly produce SO4 center dot- and gradually generate <middle dot>OH. The O-1(2) exposure showed a rapid increasing trend and the largest total exposure, while its contribution to AN degradation was small. Ball milling time and BMCS dosage demonstrated significant effect on the exposure of <middle dot>OH and O-1(2). The main active sites for BMCS to activate PMS were iron oxides, defective carbon and oxygen-containing functional groups. This study provides a green and low-cost process for value-added transformation of pyrolytic residue of oil sand (PROS), so as to promote PROS treatment mode from harmless disposal to resource utilization.