title: Degradation of diclofenac by advanced oxidation and reduction processes: kinetic studies, degradation pathways and toxicity assessments.
abstract: Many pharmaceutical compounds and metabolites are found in surface and ground waters suggesting 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 diclofenac sodium and model compound (2, 6-dichloraniline) with the two major AO/RP radicals: the hydroxyl radical (•OH) and hydrated electron (e(aq)(-)). The bimolecular reaction rate constants (M(-1) s(-1)) for diclofenac for •OH was (9.29 ± 0.11) × 10(9), and for e(-)(aq) was (1.53 ± 0.03) ×10(9). To provide a better understanding of the decomposition of the intermediate radicals produced by hydroxyl radical reactions, transient absorption spectra are observed from 1 - 250 μs. In addition, preliminary degradation mechanisms and major products were elucidated using (60)Co γ-irradiation and LC-MS. The toxicity of products was evaluated using luminescent bacteria. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime.
authors: Chinese Research Academy of Environmental Sciences, Beijing, 100012, P R China.
authors: Hui
authors: H
authors: Yu
authors: Er
authors: E
authors: Nie
authors: Jun
authors: J
authors: Xu
authors: Shuwen
authors: S
authors: Yan
authors: William J
authors: WJ
authors: Cooper
authors: Weihua
authors: W
authors: Song
mesh_terms: D000042:Absorption; D000818:Animals; D002417:Cattle; D004008:Diclofenac / Q000737:chemistry* / Q000633:toxicity*; D004583:Electrons; D005720:Gamma Rays; D054879:Halogenation / Q000187:drug effects / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D013057:Spectrum Analysis; D018675:Toxicity Tests; D014733:Vibrio / Q000187:drug effects / Q000254:growth & development
chemical_list: D004008:Diclofenac; D017665:Hydroxyl Radical