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 γ-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 (Γ max) was ranked the order of IO-250>IO-320>γ-FeOOH>IO-420>IO-520 and the adsorption equilibrium constant (K a) followed the order of IO-250>IO-520>γ-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 () for γ-FeOOH, IO-250, IO-320, IO-420 and IO-520 were 1.8, 1.6, 3.5, 3.0 and 0.8mM, respectively. The photodegradation of orange I in the presence of optimal was ranked as the order of γ-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 and iron oxides. [Copyright &y& Elsevier]