Degradation of the fluoroquinolone enrofloxacin by electrochemical advanced oxidation processes based on hydrogen peroxide electrogeneration

Solutions of the veterinary fluoroquinolone antibiotic enrofloxacin in 0.05M Na2SO4 of pH 3.0 have been comparatively degraded by electrochemical advanced oxidation processes such as anodic oxidation with electrogenerated H2O2 (AO-H2O2). electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF) at constant current density The study has been performed using all undivided stirred tank reactor of 100 ml and a batch recirculation flow plant of 2.51 with an undivided filter-press cell coupled to a solar photoreactor, both equipped with a Pt or boion-doped diamond (BDD) anode and a carbon-polytetrafluoroethylene gas diffusion cathode to generate 11202 from O-2 reduction In EF, PEF and SPEF, hydroxyl radical ((OH)-O-center dot) is formed from Fenton's reaction between added catalytic Fe2+ and generated H2O2. Almost total decontamination of enrofloxacin solutions is achieved in the stirred tank reactor by SPEF with BDD The use of the batch recirculation flow plant showed that this process is the most efficient and can be viable for industrial application, becoming snore economic and yielding higher mineralization degree with raising antibiotic content. This is feasible because organics are quickly oxidized with (OH)-O-center dot formed front Fenton's reaction and at BDD from water oxidation, combined with the fast photolysis of complexes of Fe(III) with generated carboxylic acids under solar irradiation The lower intensity of UVA irradiation used in PEF with BDD causes a slower degradation. EF with BDD is less efficient since (OH)-O-center dot cannot destroy the most persistent Fe(III)-oxalate and Fe(III)-oxalate complexes AO-H2O2 with BDD yields the poorest mineralization because pollutants are only removed with (OH)-O-center dot generated at BDD. All procedures are less potent using Pt as anode due to the lower production of (OH)-O-center dot at its surface Enrofloxacin decay always follows a pseudo first-order reaction Its primary aromatic by-products and short intermediates including polyols. ketones, carboxylic acids and N-derivatives are detected by GC-MS and chromatographic techniques The evolution of F-, NO3- and NH4+ ions released to the medium during each process is also determined (C) 2009 Elsevier Ltd All rights reserved