Anodic oxidation of ciprofloxacin using different graphite felt anodes: Kinetics and degradation pathways

Ciprofloxacin (CIP) is ubiquitous in the environment which poses a certain threat to human and ecology. In this investigation, the physical and electrochemical properties of graphite felt (GF) anodes which affected the anodic oxidation (AO) performance, and the CIP removal effect of GF were evaluated. The GFs were used as anodes for detection of center dot OH with coumarin (COU) as molecule probe and removal of CIP in a 150 mL electrolytic cell with Pt cathode (AO-GF/Pt system). The results showed that hydrophilic GF (B-GF) owned higher sp(3)/sp(2) and more oxygen-containing and nitrogen-containing functional groups than the hydrophobic GF (A-GF). Moreover, B-GF possessed higher oxygen evolution potential (1.12 V), more active sites and stronger center dot OH generation capacity. Above mentioned caused that B-GF exhibited more superior properties for CIP removal. The best efficiencies (96.95%, 99.83%) were obtained in the AO-B-GF/Pt system at 6.25 mA cm(-2) after 10 min (k(1), 0.356 min(-1)) and 60 min (k(2), 0.224 min(-1)), respectively. Furthermore, nine degradation pathways of CIP in AO-B-GF/Pt system were summarized as the cleavage of the piperazine ring, cyclopropyl group, quinolone ring and F atom by center dot OH. It provides new insights into the removal and degradation pathways of CIP with GF in AO system.

Automated summary

This study evaluated the physical and electrochemical properties of graphite felt (GF) anodes that affect anodic oxidation (AO) performance, as well as the CIP removal effect. The results showed that hydrophilic GF with higher oxygen evolution potential and stronger center dot OH generation capacity exhibited superior CIP removal properties. Additionally, nine degradation pathways of CIP were identified in the GF-based AO system, providing new insights into its removal and degradation mechanisms.