title: Kinetic modeling of the radiolytic degradation of Acid Orange 7 in aqueous solutions.
abstract: The degradation of Acid Orange 7 (AO7) in aqueous solutions induced by gamma-ray irradiation was investigated in terms of both the disappearance of parent molecule (decoloration) and the degree of mineralization. The disappearance of AO7 followed pseudo first-order kinetics, whereas its mineralization could be described by zero-order kinetics. The pseudo first-order degradation rate constants were found to be proportional to irradiation dose rates and the reciprocals of initial AO7 concentrations. Based on the experimental results and a reaction analysis on the steady-state radiolysis of aerated aqueous solutions, a kinetic model was developed for describing the radiolytic degradation of AO7. Moreover, with this kinetic model, the reaction rate constants of e(aq)(-) and H. with AO7 were estimated as 3.0 x 10(9) and 8.4 x 10(9) x L mol(-1) s(-1), respectively. Taking the relative contributions of oxidative and reductive species to AO7 degradation into account, oxidative radiolysis proved to be a better approach for the degradation of AO7.
authors.affiliation: Department of Chemistry, University of Science & Technology of China, Hefei, Anhui 230026, China.
authors.forename: Shu-Juan
authors.initials: SJ
authors.lastname: Zhang
authors.forename: Han-Qing
authors.initials: HQ
authors.lastname: Yu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D001391:Azo Compounds / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D001557:Benzenesulfonates; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010777:Photochemistry / Q000379:methods*; D014466:Ultraviolet Rays; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; C014722:2-naphthol orange