title: Degradation kinetics and mechanism of β-lactam antibiotics by the activation of H2O2 and Na2S2O8 under UV-254nm irradiation.
abstract: The extensive production and usage of antibiotics have led to an increasing occurrence of antibiotic residuals in various aquatic compartments, presenting a significant threat to both ecosystem and human health. This study investigated the degradation of selected β-lactam antibiotics (penicillins: ampicillin, penicillin V, and piperacillin; cephalosporin: cephalothin) by UV-254nm activated H2O2 and S2O8(2-) photochemical processes. The UV irradiation alone resulted in various degrees of direct photolysis of the antibiotics; while the addition of the oxidants improved significantly the removal efficiency. The steady-state radical concentrations were estimated, revealing a non-negligible contribution of hydroxyl radicals in the UV/S2O8(2-) system. Mineralization of the β-lactams could be achieved at high UV fluence, with a slow formation of SO4(2-) and a much lower elimination of total organic carbon (TOC). The transformation mechanisms were also investigated showing the main reaction pathways of hydroxylation (+16Da) at the aromatic ring and/or the sulfur atom, hydrolysis (+18Da) at the β-lactam ring and decarboxylation (-44Da) for the three penicillins. Oxidation of amine group was also observed for ampicillin. This study suggests that UV/H2O2 and UV/S2O8(2-) advanced oxidation processes (AOPs) are capable of degrading β-lactam antibiotics decreasing consequently the antibiotic activity of treated waters.
authors.affiliation: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Department of Civil and Environmental Engineering and Nireas-International Water Research Centre, School of Engineering, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Xuexiang
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, United States.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mezyk
authors.affiliation: Department of Civil and Environmental Engineering and Nireas-International Water Research Centre, School of Engineering, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Irene
authors.initials: I
authors.lastname: Michael
authors.affiliation: Department of Civil and Environmental Engineering and Nireas-International Water Research Centre, School of Engineering, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Despo
authors.initials: D
authors.lastname: Fatta-Kassinos
authors.affiliation: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Department of Civil and Environmental Engineering and Nireas-International Water Research Centre, School of Engineering, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus. Electronic address: dionysios.d.dionysiou@uc.edu.
authors.forename: Dionysios D
authors.initials: DD
authors.lastname: Dionysiou
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D010782:Photolysis; D017670:Sodium Compounds / Q000737:chemistry* / Q000528:radiation effects; D013431:Sulfates / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays; D047090:beta-Lactams / Q000032:analysis / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D017670:Sodium Compounds; D013431:Sulfates; D047090:beta-Lactams; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; C024625:sodium persulfate
keywords: Hydrogen peroxide; Persulfate; Radical reaction mechanism; UV-254nm; β-Lactam antibiotics