FeCo2O4@CNT/PVDF catalytic spheres as peroxymonosulfate activator for levofloxacin decontamination: Catalytic mechanism, ecotoxicity evolution and degradation pathways

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) for antibiotics removal in aqueous environments are now widely investigated, but the separation of the powdered catalysts from the water at the end of reaction is a major problem that hinders the large-scale application of PMS-based catalytic systems. In this work, based on the synthesis of FeCo2O4@CNT, the FeCo2O4@CNT/polyvinylidene fluoride (PVDF) catalytic spheres (CSs) with a diameter of 3 mm was further fabricated by phase transition method, which as peroxymonosulfate activator not only could remove 95.68 % of LVF (10 mg/L) within 60 min, but also could be easily separated from water. The various characterization results show that FeCo2O4@CNT is mainly distributed in the interior of CSs, LVF and PMS enter the interior through the surface pore structure of CSs and undergo oxidation reactions. The non-free radical pathway coupled with radical pathway contributed to the degradation of LVF where the 1O2 was the major ROS. Meanwhile, the possible degradation pathways of LVF were proposed based on the identification by LC-MS for intermediates and the Toxicity Estimation Software Tool (T. E. S. T) was adopted to evaluate their ecotoxicity evolution. The degradation efficiency of catalytic sphere system for LVF can still be maintained at about 80 % after 20 h of continuous reaction or 5 cycles batch experiments, demonstrating the stability and recoverability of CSs. In addition, simple aqueous cleaning and subsequent standing treatment could help CSs recover to the original catalytic level. Thus, this work provides a promising material for the future wastewater treatment.