Study of Oxidative Degradation and Mineralization Kinetics and Oxidation Products of Ofloxacin in Water via Electro-Fenton Method with Pt Anode, and Biodegradation Optimization

Abstract

The oxidative degradation of an antibiotic, Ofloxacin (OFX), has been investigated using the electro-Fenton (EF) process with a constant current between 100 and 500 mA and a carbon-felt cathode. The kinetics of oxidative degradation and the efficiency of mineralization were examined about the applied current and catalyst (Fe²⁺) concentration. The absolute rate constant for the oxidation of OFX by hydroxyl radical was determined using the competition kinetic approach as 3.04 ± 0.19 × 10⁹ M^–1s^–1. For efficient degradation of OFX at the relevant operating conditions, the ideal current value is 400 mA at a concentration of the catalyst (Fe²⁺) at 0.10 mM. After 6 h of electrolysis, in the present study, it is demonstrated that several cathodes, including carbon felt (CF), carbon-graphite (CG) and stainless steel (SS), had an impact on the electrochemical oxidation of the organic contaminant, OFX. A high level of mineralization (>97%) was attained. The development of F⁻, \({\text{NH}}_{{\text{4}}}^{{\text{ + }}}\) and \({\text{NO}}_{{\text{3}}}^{ - }\) ions was also monitored and their evolution during their release into the medium was discussed. Several intermediate products were identified using LC-MS/MS (liquid chromatography-mass spectrometry) and HPLC (High-performance liquid chromatography) analyses. Based on the identity of these products, a feasible route for the mineralization process is proposed. Finally, biodegradability was studied and the results indicated the following ratio of biological oxygen demand within 5 days to chemical oxygen demand BOD₅/COD through OFX mineralization by EF treatment for the possibility of evaluating the combination of electro-Fenton and biological treatment.