Acid Orange II degradation through a heterogeneous Fenton-like reaction using Fe–TiO2 nanotube arrays as a photocatalyst

Abstract

The photocatalytic degradation of the non-biodegradable azo dye Acid Orange II (AO II) was performed via a heterogeneous Fenton-like process using Fe incorporated TiO₂ nanotube arrays (Fe–TiO₂ NTAs) as a photocatalyst in the presence of H₂O₂ under UV irradiation. Fe–TiO₂ NTAs were prepared by an ultrasound-assisted impregnating-calcination method. The effects of reaction conditions including the amount of Fe incorporated into TiO₂ NTAs, initial concentration of H₂O₂, and initial pH of the AO II solution on the photocatalytic degradation rate of AO II were investigated. The results revealed that the Fe–TiO₂ NTAs prepared by ultrasonic deposition for 25 min exhibited the highest photocatalytic activity compared with pure TiO₂ NTA and other Fe–TiO₂ NTA samples. In the presence of H₂O₂, the photocatalytic degradation rate of AO II was significantly enhanced. About 80% AO II can be decomposed at pH 2.96 by using Fe–TiO₂ NTAs prepared by ultrasonic deposition for 25 min as a photocatalyst with 3 mM H₂O₂ after 120 min of UV irradiation, which was 1.7 times higher than that without H₂O₂ (∼30%). Very interestingly, there was an obvious synergistic effect between the photocatalytic process of Fe–TiO₂ NTAs and H₂O₂ oxidation. Furthermore, the Fe–TiO₂ NTA photocatalyst exhibited excellent stability in the heterogeneous Fenton-like process. Thus, we demonstrated that the heterogeneous Fenton-like process combining the Fe–TiO₂ NTA photocatalyst with H₂O₂ oxidation has a promising application in practical wastewater treatment.