Degradation of ciprofloxacin using Fenton's oxidation: Effect of operating parameters, identification of oxidized by-products and toxicity assessment

Ciprofloxacin (CPX), a fluoroquinolone antibiotic, is found in the bulk effluents emerged from pharmaceutical industries. Its presence in the effluent may lead to toxicity to the aquatic life and antimicrobial resistance. Hence, the oxidative degradation of CPX by classical Fenton's process was investigated for the present study. The maximum CPX and total organic carbon (TOC) removal from the synthetic wastewater (initial CPX concentration = 100 mg L-1) were 70% and 55%, respectively, under the best reaction conditions ([H2O2]:[Fe2+] = 10, stoichiometric H2O2 concentration = 14.2 mM and initial wastewater pH = 3.0). Five major degradation products could be identified by high resolution liquid chromatography mass spectrometry (HR LC-MS) which could have resulted by the occurrence of decarboxylation, defluorination, hydroxylation and cleavage of the piperazine ring. The time based detection of ferrous and ferric ions in aqueous phase confirmed the CPX degradation by hydroxyl radicals. A pathway has been proposed for CPX degradation by Fenton's process based on the kinetic decay and/or evolution profiles of CPX and intermediates as well as the release of inorganic ions into the aqueous solution. It was indicated from the rapid respirometric test that the wastewater toxicity was lowered after Fenton's treatment. (C) 2017 Elsevier Ltd. All rights reserved.