Electro-Fenton degradation of antibiotic ciprofloxacin (CIP): Formation of Fe3+-CIP chelate and its effect on catalytic behavior of Fe2+/Fe3+ and CIP mineralization

5 years ago

Electro-Fenton degradation of antibiotic ciprofloxacin (CIP): Formation of Fe3+-CIP chelate and its effect on catalytic behavior of Fe2+/Fe3+ and CIP mineralization

This work investigated the effect of the chelation of Fe³⁺ with a fluoroquinolone (FQ) antibiotic ciprofloxacin (CIP) on the catalytic behavior of Fe³⁺/Fe²⁺ and the degradation and mineralization of CIP in electro-Fenton (EF) process using activated carbon fiber (ACF) felt cathode. First of all, effect of initial Fe²⁺ and Fe³⁺ concentrations on the degradation and mineralization of CIP in EF process was compared, while the optimal initial Fe²⁺ and Fe³⁺ contents were both verified to be 1.50mmoldm⁻³, in which 73% and 72% of initial TOC were eliminated after 360min electrolysis, respectively. Secondly, Fe³⁺-CIP chelate was produced during CIP degradation in EF process, whose predominant form was confirmed as 1:2 metal-ligand stoichiometry. The formation of Fe³⁺-CIP chelate had no obvious inhibition on the degradation and mineralization of CIP due to the efficient Fe³⁺ reduction on the ACF cathode with excellent catalytic feature. About 17% and 35% of initial 1.50mmoldm⁻³ Fe³⁺ were reduced to Fe²⁺ at 18mAcm⁻² in ultrapure water and 200mgdm⁻³ CIP solutions during 30min pre-aeration of EF process, respectively, while higher Fe²⁺ concentration was maintained for initial 1.50mmoldm⁻³ Fe³⁺ during CIP degradation. Finally, the evolution of F⁻, NH4 ⁺ and NO3 ⁻ ions released to the acidic medium were determined, as well as the formation of short-chain carboxylic acid (oxalic, oxamic and formic acids). Eight aromatic intermediates were identified using UPLC-QTOF-MS/MS, and a feasible mineralization pathway was proposed.

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DOI: S0013468617320443