MoS2 coupled with ball milling co-modified sludge biochar to efficiently activate peroxymonosulfate for neonicotinoids degradation: Dominant roles of SO4•-, 1O2 and surface-bound radicals

An efficient catalyst of molybdenum disulfide (MoS2) coupled with ball milling modified sludge biochar (BMSBC) was prepared to efficiently activate peroxymonosulfate (PMS) for neonicotinoids elimination. As expected, 95.1% of imidacloprid (IMI) was degraded by PMS/BMSBC system within 60 min and it was accompanied by the outstanding mineralization rate of 71.9%. The superior pore structures, rich defects, oxygen-containing functional groups and grafted MoS2 on BMSBC offered excellent activation performance for PMS. The influencing factor experiments demonstrated that PMS/BMSBC system performed high anti-interference to wide pH range and background constituents (e.g., inorganic ions and humic acid). Quenching experiments and electron paramagnetic resonance analysis revealed that SO4 center dot-, O-1(2), and surface-bound radicals played critical roles in IMI degradation. Electron donors on biochar activated PMS, producing surface radicals. The lone pair electrons within the Lewis basic site of C=O on BMSBC enhanced PMS decomposition by facilitating the cleavage of the -O-O- bond in PMS to release O-1(2). The activation process of PMS by MoS2 accelerated the oxidation of Mo (IV) to Mo (VI) to generate SO4 center dot-. Based on the transformed products (TPs), four degradation pathways of IMI in PMS/BMSBC system were suggested, and all TPs toxicity levels were lower than that of IMI by ECOSAR analysis. Additionally, BMSBC exhibited outstanding sustainable catalytic activity towards PMS activation with the well accepted degradation rate of 71.3% for IMI even after five reuse cycles. PMS/BMSBC system also exhibited satisfactory degradation rates (>71.8%) for IMI in various real waters (e.g., sewage effluent and livestock wastewater). Furthermore, PMS/BMSBC system also offered a favorable broad-spectrum elimination performance for other typical neonicotinoids (e.g., thiamethoxam, clothianidin, thiacloprid) with the degradation rates over 98%. This study has developed a desirable neonicotinoids purification technology in view of its high degradation/mineralization rate, outstanding detoxification performance, satisfied anti-interference to ambient conditions and sustainable sludge management.