Photo-Catalyzed p-Nitrophenol Degradation in Aqueous Dispersions of Ferrihydrite and H2O2

Nitrophenols are hazardous and toxic to living organisms. For this study, ferrihydrite was prepared to test its capabilities for p-nitrophenol degradation. A ferrihydrite particle prepared in neutral environmental conditions is sphere-like with a diameter of 2-4 nm and its total surface area is approximately 229 m(2).g(-1). The combination of ferrihydrite and trace H2O2 is effective for the degradation of p-nitrophenol under simulated sunlight irradiation. Hydroquinone, the initial intermediate of p nitrophenol decomposition, autocatalyses the subsequent degradation of p-nitrophenol because it accelerates the photo-reductive dissolution of ferrihydrite. The effect of key operating parameters such as ferrihydrite dosage, initial solution pH and H2O2 dosage were also studied on the photocatalytic degradation of p-nitrophenol. The results indicate that the combination of 0.2 g.L-1 ferrihydrite, 0.45 mmol.L-1 H2O2 is highly efficient for the degradation of p-nitrophenol (0.15 mmol.L-1) at pH 2.5 similar to 3.0. A ferrihydrite was reused several times, still keeping its original photocatalysis.