title: Toxicity removal assessments related to degradation pathways of azo dyes: Toward an optimization of Electro-Fenton treatment.
abstract: The degradation pathway of Acid Orange 7 (AO7) by Electro-Fenton process using carbon felt cathode was investigated via HPLC-UV and LC-MS, IC, TOC analysis and bioassays (Vibrio Fischeri 81.9% Microtox(®) screening tests). The TOC removal of AO7 reached 96.2% after 8 h treatment with the optimal applied current density at -8.3 mA cm(-2) and 0.2 mM catalyst concentration. The toxicity of treated solution increased rapidly to its highest value at the early stage of electrolysis (several minutes), corresponding to the formation of intermediate poisonous aromatic compounds such as 1,2-naphthaquinone (NAPQ) and 1,4-benzoquinone (BZQ). Then, the subsequent formation of aliphatic short-chain carboxylic acids like acetic acid, formic acid, before the complete mineralization, leaded to a non-toxic solution after 270 min for 500 mL of AO7 (1 mM). Moreover, a quantitative analysis of inorganic ions (i.e. ammonium, nitrate, sulfate) produced during the course of degradation could help to verify molar balance with regard to original nitrogen and sulfur elements. To conclude, a clear degradation pathway of AO7 was proposed, and could further be applied to other persistent pharmaceuticals in aquatic environment.
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Thi Xuan Huong
authors.initials: TXH
authors.lastname: Le
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Thi Van
authors.initials: TV
authors.lastname: Nguyen
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Zoulkifli Amadou
authors.initials: ZA
authors.lastname: Yacouba
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Zoungrana
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Florent
authors.initials: F
authors.lastname: Avril
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Eddy
authors.initials: E
authors.lastname: Petit
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Mendret
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Bonniol
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Mikhael
authors.initials: M
authors.lastname: Bechelany
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France.
authors.forename: Stella
authors.initials: S
authors.lastname: Lacour
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France. Electronic address: Geoffroy.Lesage@umontpellier.fr.
authors.forename: Geoffroy
authors.initials: G
authors.lastname: Lesage
authors.affiliation: IEM (Institut Européen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Université de Montpellier, Place E. Bataillon, F-34095, Montpellier, France. Electronic address: Marc.Cretin@umontpellier.fr.
authors.forename: Marc
authors.initials: M
authors.lastname: Cretin
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D001391:Azo Compounds / Q000032:analysis / Q000633:toxicity*; D001557:Benzenesulfonates / Q000032:analysis / Q000633:toxicity*; D002384:Catalysis; D004396:Coloring Agents / Q000032:analysis / Q000633:toxicity*; D004566:Electrodes; D004572:Electrolysis; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D004396:Coloring Agents; C045076:Fenton's reagent; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; D007501:Iron; C014722:2-naphthol orange
keywords: Acid Orange 7; Advanced oxidation process; Carbon felt; Mineralization; Toxicity