Cerium/Zif-67 Derivatives for Degradation of Levofloxacin by Catalyzing O3/Pms: Performance Evaluation, Mechanistic Study and Toxicity Analysis

Abstract

Antibiotics that permeate aquatic environments present significant risks to both ecosystems and human health. In this study, we employed the techniques of room temperature aqueous solution precipitation and high-temperature calcination to fabricate Ce/ZIF-67 derivatives. Furthermore, we pioneered the establishment of a Co3O4/CeO2/O3/PMS system. The optimized parameters revealed that under specific conditions—a molar ratio of Co to Ce of 1, calcination temperature at 300 ℃, catalyst dosage at 0.15 g/L, PMS dosage at 0.15 g/L, and an ozone inflow rate of 0.20 L/min — a 10 mg/L Levofloxacin (LEF) solution could reach rapid degradation (97.2%) and effective mineralization (40.4%). Subsequent investigations identified the primary active substances, intermediates, and reaction mechanism in the Co3O4/CeO2/O3/PMS system. Evidence from Electron Paramagnetic Resonance (EPR) and quenching experiments indicates that the radicals SO4·-, OH·, O2·- and 1O2 contribute to the degradation process, with 1O2 assuming a preeminent role. Applying High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS), we discovered that the principal degradation mechanisms for LEF encompass the cleavage and subsequent loss of the piperazine, quinolone, and morpholine rings, in addition to decarboxylation and defluorination reactions. We subsequently studied the acute toxicity, bioconcentration factor, developmental toxicity, and mutagenicity of LEF and its intermediate products through the Toxicity Estimation Software Tool (T.E.S.T.). Our findings reveal a notable reduction in the toxicity of the intermediate products relative to LEF. Final experimental observations demonstrate that the removal rate of Co3O4/CeO2 sustains above 90% after five cycles of reactions, indicative of excellent recyclability and stability. This research enriches the understanding of ZIF-67 derivative-catalyzed degradation of organic pollutants, and provides valuable reference data concerning the degradation pattern and toxicity alterations of emerging pollutants in the O3/PMS system.

Keywords: Co3O4/CeO2, O3/PMS, Levofloxacin, ROSs, Toxicity