title: Application of electrochemically generated ozone to the discoloration and degradation of solutions containing the dye Reactive Orange 122.
abstract: Aqueous solutions containing the commercial azo dye Reactive Orange 122 (RO122) were ozonated in acid and alkaline conditions. Ozone was electrochemically generated using a laboratory-made electrochemical reactor and applied using semi-batch conditions and a column bubble reactor. A constant ozone application rate of 0.25gh(-1) was used throughout. Color removal and degradation efficiency were evaluated as function of ozonation time, pH and initial dye concentration by means of discoloration kinetics and COD-TOC removal. Experimental findings revealed that pH affects both discoloration kinetics and COD-TOC removal. A single pseudo-first-order kinetic rate constant, k(obs), for discoloration was found for ozonation carried out in alkaline solutions, contrary to acidic solutions where k(obs) depends on ozonation time. COD-TOC removal supports degradation of RO122 is more pronounced for alkaline conditions. Evaluation of the oxidation feasibility by means of the COD/TOC ratio indicates that the ozonation process in both acid and alkaline conditions leads to a reduction in recalcitrance of the soluble organic matter.
authors.affiliation: Institute of Chemistry - UFU, Laboratory of Electrochemistry, Campus Santa Mônica, Av. João Naves de Avila 2160, 38400-902 Uberlândia, MG, Brazil.
authors.forename: Mário H P
authors.initials: MH
authors.lastname: Santana
authors.forename: Leonardo M
authors.initials: LM
authors.lastname: Da Silva
authors.forename: Admildo C
authors.initials: AC
authors.lastname: Freitas
authors.forename: Julien F C
authors.initials: JF
authors.lastname: Boodts
authors.forename: Karla C
authors.initials: KC
authors.lastname: Fernandes
authors.forename: Luiz A
authors.initials: LA
authors.lastname: De Faria
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010126:Ozone / Q000737:chemistry* / Q000378:metabolism; D013463:Sulfuric Acid Esters / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D013463:Sulfuric Acid Esters; D014874:Water Pollutants, Chemical; C109260:reactive orange; D010126:Ozone