Enhanced Mechanism of Electrochemical Oxidation of Antibiotic Norfloxacin using a Ti/SnO2-Sb2O3/α,β-Co-PbO2 Electrode

This study focused on the enhanced mechanism of electrochemical degradation of antibiotic norfloxacin (NOR) using a self-made Ti/SnO2-Sb2O3/α,β-Co-PbO2 electrode. The electrode characterization, reaction mechanism, degradation performance, and toxicity assessment were studied. In contrast to the conventional Ti/SnO2-Sb2O3/α,β-PbO2 electrode, our prepared Co-doped PbO2 electrode showed the characteristics of more compact surface, smaller crystal size, higher oxygen evolution potential (OEP) and an increased yield of ·OH concentration. The application of Co-doped PbO2 electrode for the electrochemical oxidation of NOR was systematically analyzed. The optimal operating parameters were found to be Na2SO4 concentration of 0.1 mol L−1, initial NOR concentration of 50 mg L−1, initial pH of 5 and current density of 20 mA cm−2. Under these conditions, NOR, chemical oxygen demand (COD) and total organic carbon (TOC) removals reached 85.29%, 43.65% and 41.89% after 60 min of electrolysis, respectively. Through the intermediates detected during the electrochemical treatment process, a reaction pathway involving decarboxylation, defluorination and piperazine ring-opening was proposed. Finally, the toxicity assessment of the treated NOR solution towards Vibrio fischeri rapidly fell to non-toxicity and even reached to negative values after 50 min of electrolysis, indicating that electrochemical oxidation of NOR is an effective approach to reduce its toxicity to environmental ecosystem.