Activate persulfate for catalytic degradation of adsorbed anthracene on coking residues: Role of persistent free radicals

Abstract

Carbonaceous residues and polycyclic aromatic hydrocarbons (PAHs) are discharged simultaneously during the coke production. Chemical-structural properties of coking residues, such as coke powder, tar slag, and fly ash, were characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area, scanning electron microscopy (SEM), and electron paramagnetic resonance (EPR) techniques. Highly disorder amorphous structures with abundant of oxygen functionalities and persistent free radicals were observed for coke powder and tar slag. The potential activation of persistent free radicals (PFRs) on persulfate to generate reactive oxygen species (ROS) and induce the degradation of anthracene (ANT) was studied. The formation of H2O2 and decay rate of ANT highly correlate with the spin densities of bounded PFRs in coking residues. EPR technique combined with different radical scavengers was applied to investigate the generation of ROS. The results suggest that PFRs provide the electron to persulfate or/and O2, inducing the formation of SO4−, H2O2, and OH. The produced ROS then back-reacts with adsorbed organic compounds, such as ANT, resulting in its oxidation and/or complete mineralization. The obtained results are relevant to the fate of adsorbed pollutants in coke-polluted soil environments and shed light on the development of remediation technologies for solid waste released during the coke production.