title: Free-radical destruction of beta-lactam antibiotics in aqueous solution.
abstract: Many pharmaceutical compounds and metabolites are being found in surface and ground waters, indicating their ineffective removal by conventional wastewater treatment technologies. Advanced oxidation/reduction processes (AO/RPs), which utilize free-radical reactions to directly degrade chemical contaminants, are alternatives to traditional water treatment. This study reports the absolute rate constants for reaction of three beta-lactam antibiotics (penicillin G, penicillin V, amoxicillin) and a model compound (+)-6-aminopenicillanic acid with the two major AO/RP reactive species: hydroxyl radical ((*)OH) and hydrated electron (e(-)aq). The bimolecular reaction rate constants (M(-1) s(-1)) for penicillin G, penicillin V, amoxicillin, and (+)-6-aminopenicillanic acid for (*)OH were (7.97 +/- 0.11) x 10(9), (8.76 +/- 0.28) x 10(9), (6.94 +/- 0.44) x 10(9), and (2.40 +/- 0.05) x 10(9) and for e(-)aq were (3.92 +/- 0.10) x 10(9), (5.76 +/- 0.24) x 10(9), (3.47 +/- 0.07) x 10(9), and (3.35 +/- 0.06) x 10(9), respectively. To provide a better understanding of the decomposition of the intermediate radicals produced by hydroxyl radical reactions, transient absorption spectra were observed from 1 to 100 micros. In addition, preliminary degradation mechanisms and major products were elucidated using (137)Cs gamma irradiation and LC-MS. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime.
authors.affiliation: Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, California 92697-2175, USA. wsong@uci.edu
authors.forename: Weihua
authors.initials: W
authors.lastname: Song
authors.forename: Weisang
authors.initials: W
authors.lastname: Chen
authors.forename: William J
authors.initials: WJ
authors.lastname: Cooper
authors.forename: John
authors.initials: J
authors.lastname: Greaves
authors.forename: George E
authors.initials: GE
authors.lastname: Miller
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D012996:Solutions; D013997:Time Factors; D014867:Water / Q000737:chemistry*; D047090:beta-Lactams / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D005609:Free Radicals; D012996:Solutions; D047090:beta-Lactams; D014867:Water; D017665:Hydroxyl Radical; D010397:Penicillanic Acid; C004408:aminopenicillanic acid