Photocatalytic decolourization of the X3B textile dye in aqueous solutions using iron-rich montmorillonite

Abstract

Photocatalytic decolourization of textile dye X3B in aqueous solutions was investigated, using iron-rich montmorillonite (MMt, 2·24%Fe2O3) under a 15 W low-pressure UV lamp (λ = 254  nm, I = 48·4 μW/cm2). Hydroxyl radicals (•OH) were detected by tert-butyl alcohol (TBA) in aqueous MMt suspensions under UV irradiation and were found to be responsible for the degradation of X3B. Free iron ions dissolved in MMt suspensions, structural iron in the MMt solid, and the charged surface of nano clay are responsible for hydroxyl radical (•OH) production. Low pH values are favorable for the decolourization of X3B. The •OH concentration increased with increasing aqueous MMt concentrations in the range of 0  –  2·0  g/L; higher concentrations, for example, 5·0  g/L MMt, inhibited the •OH production. The addition of oxalate was favorable for X3B photodegradation in acid-washed MMt suspensions. This study shows that iron-rich MMt is a potential photocatalyst for the treatment of dye wastewater.