Feasibility and mechanism of p-nitrophenol decomposition in aqueous dispersions of ferrihydrite and H2O2 under irradiation

This investigation illustrates the fact that the effective decomposition of p-nitrophenol (p-NP) in H2O2/ferrihydrite (FH) dispersion under irradiation is a homogeneous Fenton-like reaction in a heterogeneous system. The decomposition of p-NP is initiated from the photo-dissolution of FH into aqueous Fe(III) that reacts slowly with H2O2 to generate hydroxyl radical. Hydroquinone, the initial intermediate of p-NP decomposition, auto-accelerates the subsequent decomposition of p-NP due to its acceleration of the photo-reductive dissolution of FH. The effect of key operating parameters such as FH dosage, initial solution pH and H2O2 dosage was also studied on the photo-induced decomposition of p-NP. The results indicate that the combination of FH and H2O2 with a molar ratio of 1:0.225 is highly efficient for the decomposition of p-NP (0.15 mM) at pH 2.5-3.0.