title: Electro-oxidation of the dye azure B: kinetics, mechanism, and by-products.
abstract: In this work, the electrochemical degradation of the dye azure B in aqueous solutions was studied by electrochemical advanced oxidation processes (EAOPs), electro-Fenton, and anodic oxidation processes, using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with H₂O₂ electrogeneration. The higher oxidation power of the electro-Fenton (EF) process using BDD anode was demonstrated. The oxidative degradation of azure B by the electrochemically generated hydroxyl radicals ((•)OH) follows a pseudo-first-order kinetics. The apparent rate constants of the oxidation of azure B by (•)OH were measured according to pseudo-first-order kinetic model. The absolute rate constant of azure B hydroxylation reaction was determined by competition kinetics method and found to be 1.19 × 10(9) M(-1) s(-1). It was found that the electrochemical degradation of the dye leads to the formation of aromatic by-products which are then oxidized to aliphatic carboxylic acids before their almost mineralization to CO₂ and inorganic ions (sulfate, nitrate, and ammonium). The evolution of the TOC removal and time course of short-chain carboxylic acids during treatment were also investigated.
authors.affiliation: Université Paris-Est, Laboratoire Géomatériaux et Environnement, EA 4508, UPEM, 5, Bd Descartes, 77454, Marne-la-Vallée, France.
authors.forename: Hugo
authors.initials: H
authors.lastname: Olvera-Vargas
authors.forename: Nihal
authors.initials: N
authors.lastname: Oturan
authors.forename: C T
authors.initials: CT
authors.lastname: Aravindakumar
authors.forename: M M Sunil
authors.initials: MM
authors.lastname: Paul
authors.forename: Virender K
authors.initials: VK
authors.lastname: Sharma
authors.forename: Mehmet A
authors.initials: MA
authors.lastname: Oturan
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry; D001399:Azure Stains / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D018130:Diamond / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D009566:Nitrates / Q000737:chemistry; D010084:Oxidation-Reduction; D010984:Platinum / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry
chemical_list: D064751:Ammonium Compounds; D001399:Azure Stains; D002264:Carboxylic Acids; D004396:Coloring Agents; D009566:Nitrates; D013431:Sulfates; D017665:Hydroxyl Radical; D010984:Platinum; D018130:Diamond; C025819:Azure B; D006861:Hydrogen Peroxide; D001895:Boron