Photodegradation of Methylene Blue in Fe₂O₃–Oxalate Suspension Under UV Light Irradiation

The aim of this study was to investigate the photodegradation of organic pollutants in natural environment with co-existence of iron oxides and oxalic acid. Methylene Blue (MB) was selected as a model pollutant while Fe₂O₃ was selected as iron oxide. Commercial Fe₂O₃ was calcined at 300°C, 400°C and 500°C and was used to degrade MB in oxalate solutions of different concentration under UV radiation. Adsorption of MB on the surface of calcined Fe₂O₃ was studied and 30 minutes was required to reach the adsorption equilibrium. The effect of the initial concentration of oxalic acid, initial concentration of MB and calcined temperature of Fe₂O₃ on photodegradation of MB in the Fe₂O₃–oxalate suspension under UV light irradiation was investigated. Oxalic acid plays a very important role, no significant degradation of MB was found in absence of oxalic acid in the suspension. But excess concentration of oxalic acid decreases the degradation. Photodegradation of MB increases with increasing calcined temperature of Fe₂O₃ and decreases with increase in MB concentration. Since this process does not require the addition of hydrogen peroxide and shows good efficiency under UV irradiation, it is an economically viable method for pre-treating wastewater containing dye.