High-efficiency degradation of norfloxacin by cathodic micro-arc plasma electrolysis:Optimization of operation parameters and investigation on kinetics

Abstract

In this work, the norfloxacin antibiotic (NOR) in simulated wastewater solution was rapidly degraded by a novel cathodic micro-arc plasma electrolysis (CMPE) treatment within 20 min. The effects and kinetics of initial pH value of solution, supporting electrolyte, and applied voltage on this NOR degradation process were systematically investigated. The intermediate products are analyzed by a Liquid Chromatograph-Mass Spectrometer (LC-MS), and the possible degradation pathways in the NOR degradation process were proposed. The results obtained showed that the NOR removal efficiency increased with the increase of the initial pH value of the solution. When KCl was employed as the supporting electrolyte instead of KNO3 and K2SO4, the removal efficiency of NOR is the highest. In addition, the removal efficiency is not significantly different at 340 V, 380 V, and 420 V, but it is more beneficial to the removal of chemical oxygen demand (COD) and the increase of average current efficiency (ACE) at 380 V. Furthermore, under the optimized operating parameters for the initial pH value of 9, supporting electrolyte of KCl, and applied voltage of 380 V, the 100 mg/L NOR solution can be completely removed within 10 min, and the energy yield and average current efficiency were 0.385 g (kW⋅h)-1 and 0.118. Further, it is found that the degradation pathways of NOR mainly include the piperazine ring opening, hydroxylation, defluorination, and quinoline ring transformation. Overall, this study provides a high-efficiency and novel technique for the NOR degradation treatment.