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This work investigated the effect of the chelation of Fe 3+ with a fluoroquinolone (FQ) antibiotic ciprofloxacin (CIP) on the catalytic behavior of Fe 3+ /Fe 2+ 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 Fe 2+ and Fe 3+ concentrations on the degradation and mineralization of CIP in EF process was compared, while the optimal initial Fe 2+ and Fe 3+ contents were both verified to be 1.50 mmol dm −3 , in which 73% and 72% of initial TOC were eliminated after 360 min electrolysis, respectively. Secondly, Fe 3+ -CIP chelate was produced during CIP degradation in EF process, whose predominant form was confirmed as 1:2 metal-ligand stoichiometry. The formation of Fe 3+ -CIP chelate had no obvious inhibition on the degradation and mineralization of CIP due to the efficient Fe 3+ reduction on the ACF cathode with excellent catalytic feature. About 17% and 35% of initial 1.50 mmol dm −3 Fe 3+ were reduced to Fe 2+ at 18 mA cm −2 in ultrapure water and 200 mg dm −3 CIP solutions during 30 min pre-aeration of EF process, respectively, while higher Fe 2+ concentration was maintained for initial 1.50 mmol dm −3 Fe 3+ during CIP degradation. Finally, the evolution of F − , NH 4 + and NO 3 − 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. [ABSTRACT FROM AUTHOR]

Solutions of 500 mL 200 mg L −1 fluoroquinolone antibiotic levofloxacin (LEVO) have been degraded by anodic oxidation (AO), AO with electrogenerated H 2 O 2 (AO–H 2 O 2 ) and electro-Fenton (EF) processes using an activated carbon fiber (ACF) felt cathode from the point view of not only LEVO disappearance and mineralization, but also biodegradability enhancement. The LEVO decay by EF process followed a pseudo-first-order reaction with an apparent rate constant of 2.37 × 10 −2 min −1 , which is much higher than that of AO or AO–H 2 O 2 processes. The LEVO mineralization also evidences the order EF > AO–H 2 O 2 > AO. The biodegradability (BOD 5 /COD) increased from 0 initially to 0.24, 0.09, and 0.03 for EF, AO–H 2 O 2 and AO processes after 360 min treatment, respectively. Effects of several parameters such as current density, initial pH and Fe 2+ concentration on the EF degradation have also been examined. Three carboxylic acids including oxalic, formic and acetic acid were detected, as well as the released inorganic ions NH 4 + , NO 3 − and F − . At last, an ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry was used to identify about eight aromatic intermediates formed in 60 min of EF treatment, and a plausible mineralization pathway for LEVO by EF treatment was proposed. [ABSTRACT FROM AUTHOR]

Oxidation of a commonly-used β-lactam pharmaceutical, cefoperazone (CFPZ), was systematically investigated by anodic oxidation (AO), AO in presence of H 2 O 2 electro-generation (AO-H 2 O 2) and electro-Fenton (EF) processes with an activated carbon fiber cathode from the biodegradability viewpoint. The degradation and mineralization rates increased in a sequence of AO < AO-H 2 O 2 < EF. Even CPFZ could be efficiently degraded in EF process, achieving complete CFPZ mineralization was rather difficult. Thereby, the biodegradability of the effluent after electrochemical pretreatment was examined to test the feasibility of the combination of electrochemical and biological processes. The results suggested that compared with AO and AO-H 2 O 2 , EF process could effectively transform the non-biodegradable CFPZ into biocompatible materials with a high BOD 5 /COD value (0.33 after 720 min), allowing the possible biotreatment for further remediation. This behavior was relatively accorded with the average oxidation state (AOS) results, evidencing the potential of EF process in enhancing the biodegradability of CFPZ. The determination of inorganic ions revealed that N in CFPZ molecular was oxidized into NH 4 + and NO 3 − ions in EF process. Oxalic, succinic, oxamic, fumaric and formic acids were also formed. Besides, six aromatic by-products were qualified and a possible pathway involving hydrolysis, hydroxylation and decarboxylation during CFPZ mineralization was proposed. Image 1 • CFPZ underwent complete degradation but partial mineralization in EF condition. • Obvious biodegradability improvement was obtained during EF process. • The feasibility of combing EF with biological treatment was demonstrated. • Aromatic intermediates, carboxylic acids and inorganic ions were determined. • A comprehensive CFPZ degradation pathway involving.•OH was proposed. [ABSTRACT FROM AUTHOR]