Degradation of pyrene in sediments based on the activation of peroxymonosulfate with nitrogen-doped magnetic biochar: Synergistic effect and mechanism

Pyrene (PYR) is a typical high molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) with potential biotoxicity and resistance to biodegradation, and the accumulation of PYR in sediments increases the risk to ecosystems. Therefore, this study evaluated the catalytic performance of nitrogen-doped magnetic biochar-activated peroxymonosulfate system (NMBC/PMS) on PYR in sediments and elucidated its mechanism. The results showed that the degradation rate of PYR in sediments by the NMBC/PMS system reached 87% at PMS= 1 x 10(-4) M, NMBC= 3.0 g/L and pH= 9, which conformed to the pseudo-first-order rate law, and the rate constant (K-obs) was 7.3 x 10(-2) h(-1). The high adsorption performance of NMBC was attributed to pi-pi electron donor -acceptor interactions (pi-pi EDA). The high degradation performance of NMBC/PMS system was attributed to the active sites generated by graphitization, magnetism, and electronegativity of NMBC, which were the key to activate PMS to degrade PYR. The results of X-ray photoelectron spectroscopy (XPS), quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that N-doping and Fe3O4-loading on NMBC synergistically promoted the degradation of PYR. In addition, the mechanism of PYR degradation by NMBC/PMS system was investigated, indicating that SO4 center dot(-), HO center dot and O-1(2) were the main reactive oxygen species. The excellent recoverability of NMBC showed its application potential. The NMBC/PMS system developed in this study provided a theoretical basis for a future multi-pathway synergistic degradation mechanism of PYR in sediments.