Degradation of Norfloxacin in saline water by synergistic effect of anode and cathode in a novel photo-electrochemical system

The removal and degradation of refractory antibiotics in saline water by electrochemical and photo-electrochemical catalysis has emerged as a worldwide research hotspot. Aiming to improve degradation performance, most of the concerned studies focus on new sophisticated materials and modification methods on the single working electrode (anode or cathode). But the synergistic effects between anode and cathode has rarely been studied, especially in photo-electrochemical system. In this work, these effects were initially developed and investigated in the photo-electrochemical system. In this work, a low-cost double-working electrodes photo-electrochemical system (TSSC-Photo) with Ti/SnO2-Sb anode and carbon black air diffusion cathode (TSSC) was constructed for Norfloxacin (NOR) degradation in saline water. The degradation efficiency, vital factors, degradation pathways were investigated. The mathematic modeling was adopted to distinguish the degradation kinetics and degradation contributions ratio from anode and cathode sides of this system. Owing to the synergistic effects of both electrodes, a rapidly complete NOR removal was achieved within 4 min and the highest TOC removal ratio reached 83.9% within 120 min. Free radicals (•Cl, •OH, etc) were considered as dominate oxidants in degradation with no activated chlorine (HClO/ClO−) detected from the electrolyte during the photo-electrolysis. The analysis based on the mathematic modeling indicated that anode acted as the only contributor (>97% of overall contribution) during the first 5 min of photo-electrolysis, whereas at the end of 120 min running, 21.4% of the total contribution came from cathode side. The remarkable performance of TSSC-Photo claimed its great capacity for organic matter degradation in saline water especially with Cl−.