Comparison of different advanced oxidation processes for the degradation of two fluoroquinolone antibiotics in aqueous solutions

In this study a comparative assessment using various advanced oxidation processes (UV/H2O2, UV/H2O2/Fe(II), O3, O3/UV, O3/UV/H2O2 and O3/UV/H2O2/Fe(II)) was attempted to degrade efficiently two fluoroquinolone drugs ENR [enrofloxacin (1-Cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinolonecarboxylic acid)] and CIP [ciprofloxacin (1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-quinoline-3-carboxylic acid)] in aqueous solutions at a concentrations of 0.15 mM for each drug. The efficiency of the applied oxidation processes (AOPs) has been estimated by the conversion of the original substrate (XENR and XCIP) and the reduction of chemical oxygen demand (COD), total organic carbon (TOC). Special emphasis was laid on the effect of varying reaction pH as well as of the applied oxidant doses on the observed reaction kinetics for each advanced oxidation processes. High degradation efficiencies, particularly in terms of rates of TOC and COD abatement, were obtained for photo-Fenton assisted ozonation [O3/UV/H2O2/Fe(II)], compared to other advanced oxidation processes. At pH 3 and 25°C best results for the degradation of both investigated drugs were achieved when 10 mM H2O2, 0.5 mM Fe(II) and an initial dose of 8.5 mg L−1 ozone were applied. In addition, the evolution of toxicity of the reaction mixtures for different AOPs has been studied by the bioluminescence test (LUMIStox 300).