Heat-activated persulfate oxidative degradation of ofloxacin: Kinetics, mechanisms, and toxicity assessment

The widespread occurrence of fluoroquinolone antibiotics, such as ofloxacin (OFX), in natural water and soil has received increasing attention in terms of their potentially dangerous impacts on public health and ecosystems. In this study, the kinetics and mechanisms of OFX degradation by heat-activated persulfate (HAP) was investigated. Results showed that OFX degradation could be achieved effectively and fitted well with the pseudo-first-order reaction model in the HAP system. The OFX degradation efficiency was dramatically enhanced with increased temperature and initial persulfate dosage and inhibited in the presence of the common coexisting water matrices (e.g., bicarbonate, chloride, and humic acid). Quenching tests and electron paramagnetic resonance studies demonstrated the simultaneous contribution of both radicals with sulfate radicals having a slightly higher effect than hydroxyl radicals in the degradation process of OFX. Various intermediates of OFX degradation were characterized using High-performance liquid chromatography-Mass spectrometry (HPLC-MS), and detailed degradation pathways of OFX were proposed. And the toxicity of OFX and its intermediate products was predicted using the Ecological Structure-Activity Relationships (ECOSAR) and Toxicity Estimation Software Tools (TEST).