Photocatalytic Degradation of Orange II in Aqueous Iron-Rich Montmorillonite Solutions

Abstract

In this work the photodegradation of orange II was carried out in the presence of iron-rich montmorillonite (MMt) (2.24% Fe2O3) using a 15-W low-pressure ultraviolet lamp (λ=254 nm, I=48.4 μW/cm2). The effects of pH, MMt dose, and dye concentration were studied. A low pH value is favorable for the decolorization of orange II. The hydroxyl radical (O•H) concentration increased with increasing concentration of MMt in aqueous solutions in the range of 0–1.5 g/L. Concentrations higher than 5.0 g/L MMt inhibited the O•H production. There was no significant decrease in photocatalytic activity when the catalyst was reused. Hydroxyl radicals were detected by tert-butyl alcohol in aqueous MMt suspensions under ultraviolet irradiation and were responsible for the degradation of orange II. Free iron ions dissolved in MMt suspensions, structural iron in the MMt structural and the charged surface of nanoclay are responsible for the hydroxyl radical (O•H) production. Free iron ions dissolved in solution plays a predominant role in the degradation of orange II. This study shows that iron-rich MMt is a potential photocatalyst for dye wastewater treatment.