Mechanism comparison of heterogeneous and electro-enhanced heterogeneous activation of peroxymonosulfate based on CoFe2O4 nanoparticles for gatifloxacin degradation

Abstract

Mechanisms for gatifloxacin (GAT) degradation had been comparative studied for CoFe₂O₄ nanoparticles (NPs) based heterogeneous catalytic reaction (HCR) and its electrochemical strengthening method (EC-HCR), as peroxymonosulfate (PMS) was used for oxidant. The results indicated that EC could significantly promote the reaction rate of HCR in 10 mins due to the acceleration of Co/Fe redox cycle and electron transfer between them, and slow down due to the isolation of catalytic active sites by adsorbate since then. Different from the dominant role of SO₄^•− in HCR system, ^•OH played a pivotal role in EC-HCR system due to the generation of high-valent metal species (HVMS), which also given it greater resistance to the coexisted anions and humic acid. Neither increasing the dosage of CoFe₂O₄ NPs nor PMS could achieve efficient mineralization of GAT (33.7 % to 41.6 %) in HCR system, while the mineralization efficiencies of GAT were reached 80.4 % and 86.4 % as the mass ratio of PMS to CoFe₂O₄ were 3:1 and 5:1, respectively. Although the similar GAT degradation pathways were observed in HCR and EC-HCR system attributed to the similar active species composition, the difference in dominant active species caused a very different detoxification effect. The harmful degradation products that presence in HCR system could be degraded in EC-HCR system, with the same CoFe₂O₄ NPs and PMS dosage. Therefore, EC-HCR can be flexibly applied to the treatment of wastewater that containing antibiotics, either detoxification or complete mineralization depends on the chemical inputs.