title: Photodegradation of orange I in the heterogeneous iron oxide-oxalate complex system under UVA irradiation.
abstract: To understand the photodegradation of azo dyes in natural aquatic environment, a novel photo-Fenton-like system, the heterogeneous iron oxide-oxalate complex system was set up with the existence of iron oxides and oxalate. Five iron oxides, including gamma-FeOOH, IO-250, IO-320, IO-420 and IO-520, were prepared and their adsorption capacity was investigated in the dark. The results showed that the saturated adsorption amount (gamma(max)) was ranked the order of IO-250 > IO-320 > gamma-FeOOH > IO-420 > IO-520 and the adsorption equilibrium constant (Ka) followed the order of IO-250 > IO-520 > gamma-FeOOH > IO-420 > IO-320. The effect of initial pH value, the initial concentrations of oxalate and orange I on the photodegradation of orange I were also investigated in different iron oxide-oxalate systems. The results showed that the photodegradation of orange I under UVA irradiation could be enhanced greatly in the presence of oxalate. And the optimal oxalate concentrations (C(ox)0) for gamma-FeOOH, IO-250, IO-320, IO-420 and IO-520 were 1.8, 1.6, 3.5, 3.0 and 0.8 mM, respectively. The photodegradation of orange I in the presence of optimal C(ox)0 was ranked as the order of gamma-FeOOH > IO-250 > IO-320 > IO-420 > IO-520. The optimal range of initial pH was at about 3-4. The first-order kinetic constant for the degradation of orange I decreased with the increase in the initial concentration of orange I. Furthermore, the variation of pH, the concentrations of Fe3+ and Fe2+ during the photoreaction were also strongly dependent on the C(ox)0 and iron oxides.
authors.affiliation: The Faculty of Agriculture, Guangxi University, Nanning 630005, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lei
authors.forename: Chengshuai
authors.initials: C
authors.lastname: Liu
authors.forename: Fangbai
authors.initials: F
authors.lastname: Li
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Li
authors.forename: Shungui
authors.initials: S
authors.lastname: Zhou
authors.forename: Tongxu
authors.initials: T
authors.lastname: Liu
authors.forename: Minghua
authors.initials: M
authors.lastname: Gu
authors.forename: Qitang
authors.initials: Q
authors.lastname: Wu
mesh_terms: D001391:Azo Compounds / Q000528:radiation effects*; D005290:Ferric Compounds / Q000737:chemistry / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D008027:Light; D010070:Oxalates / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; D005290:Ferric Compounds; D010070:Oxalates; C000499:ferric oxide; C022808:E 111