Light-induced catalytic transformation of ofloxacin by solar Fenton in various water matrices at a pilot plant: Mineralization and characterization of major intermediate products

Abstract

This work investigated the application of a solar driven advanced oxidation process (solar Fenton), for the degradation of the antibiotic ofloxacin (OFX) in various environmental matrices at a pilot-scale. All experiments were carried out in a compound parabolic collector pilot plant in the presence of doses of H2O2 (2.5 mg L(-1)) and at an initial Fe(2+) concentration of 2 mg L(-1). The water matrices used for the solar Fenton experiments were: demineralized water (DW), simulated natural freshwater (SW), simulated effluent from municipal wastewater treatment plant (SWW) and pre-treated real effluent from municipal wastewater treatment plant (RE) to which OFX had been spiked at 10 mg L(-1). Dissolved organic carbon removal was found to be dependent on the chemical composition of the water matrix. OFX mineralization was higher in DW (78.1%) than in SW (58.3%) at 12 mg L(-1) of H2O2 consumption, implying the complexation of iron or the scavenging of hydroxyl radicals by the inorganic ions present in SW. On the other hand, the presence of dissolved organic matter (DOM) in SWW and RE, led to lower mineralization per dose of H2O2 compared to DW and SW. The major transformation products (TPs) formed during the solar Fenton treatment of OFX, were elucidated using liquid chromatography-time of flight-mass spectrometry (LC-ToF-MS). The transformation of OFX proceeded through a defluorination reaction, accompanied by some degree of piperazine and quinolone substituent transformation while a hydroxylation mechanism occurred by attack of the hydroxyl radicals generated during the process leading to the formation of TPs in all the water matrices, seven of which were tentatively identified. The results obtained from the toxicity bioassays indicated that the toxicity originates from the DOM present in RE and its oxidation products formed during the photocatalytic treatment and not from the TPs resulted from the oxidation of OFX.

Impact of water matrix on the removal of micropollutants by advanced oxidation technologies

“…The water matrix components may raise a negative and/or a positive impact on the effectiveness of Fenton-based processes and the overall result depends on their balance [12,16,50]. In complex water matrices containing many species, the degradation of MPs is generally lower than in pure water when Fenton-based processes are employed, implying the use of higher doses of reactants (iron species and H2O2) [51].…”

Identification of new transformation products during enzymatic treatment of tetracycline and erythromycin antibiotics at laboratory scale by an on-line turbulent flow liquid-chromatography coupled to a high resolution mass spectrometer LTQ-Orbitrap

“…low degradability of some of the antibiotics by conventional wastewater treatment, different research groups have been focusing the study on alternative degradation processes in order to increase the removal efficiency (Konstantinou et al, 2010). However, these alternative treatments can also lead to the formation of transformation products (TPs) of the pollutants that might be either more persistent or toxic than the parent compound (Watkinson et al, 2007;Farré et al, 2008;Onesios et al, 2009;Michael et al, 2013). In this context, in order to better assess the removal efficiency of such alternative treatment methods, the detection of known and unknown compounds (including TPs) is of high importance as well as to assess their toxicity.…”

Influence of dihydroxybenzenes on paracetamol and ciprofloxacin degradation and iron(III) reduction in Fenton processes

“…6). The intermediate with m/z 330 [M + H] + was formed after hydroxyl radical attack on benzene ring in an electrophilic addition reaction and consequent release of fluoride as previously observed in photo-Fenton degradation of ofloxacin and CIP with fluoride quantification in solution (Michael et al 2013;Perini et al 2014). The MS/MS experiments of m/z 330 showed the main fragments m/z 312 and m/z 286 which correspond to the loss of water and of COO − , respectively, confirming the structure of this intermediate (Fig.…”