Partial degradation of levofloxacin for biodegradability improvement by electro-Fenton process using an activated carbon fiber felt cathode

Abstract

Solutions of 500mL 200mgL−1 fluoroquinolone antibiotic levofloxacin (LEVO) have been degraded by anodic oxidation (AO), AO with electrogenerated H2O2 (AO–H2O2) and electro-Fenton (EF) processes using an activated carbon fiber (ACF) felt cathode from the point view of not only LEVO disappearance and mineralization, but also biodegradability enhancement. The LEVO decay by EF process followed a pseudo-first-order reaction with an apparent rate constant of 2.37×10−2min−1, which is much higher than that of AO or AO–H2O2 processes. The LEVO mineralization also evidences the order EF>AO–H2O2>AO. The biodegradability (BOD5/COD) increased from 0 initially to 0.24, 0.09, and 0.03 for EF, AO–H2O2 and AO processes after 360min treatment, respectively. Effects of several parameters such as current density, initial pH and Fe2+ concentration on the EF degradation have also been examined. Three carboxylic acids including oxalic, formic and acetic acid were detected, as well as the released inorganic ions NH4+, NO3− and F−. At last, an ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry was used to identify about eight aromatic intermediates formed in 60min of EF treatment, and a plausible mineralization pathway for LEVO by EF treatment was proposed.