Photocatalytic degradation of phenol and m-nitrophenol using irradiated TiO2 in aqueous solutions

Photocatalytic degradation of single and binary phenol and m-nitrophenol (m-NP) in aqueous solutions by commercial TiO2 powders (Degussa P-25) under UV irradiation was examined. The influences of various operating parameters including the initial reactant concentration (0.13–0.71 mM), solution pH (4.1–12.7), and the presence of the second reactant on photodegradation were studied. The effect of TiO2 pre-wetting with aqueous solution on phenol photodegradation was also studied. It was shown that the degradation rates of phenol and m-NP decreased with increasing initial reactant concentrations. The optimal solution pH for the photodegradation of single phenol and m-NP was at around 7.4 and 8.9, respectively. Compared to the single systems, the photodegradation rates of phenol and m-NP in binary systems decreased, particularly when the second reactant was in excess. Moreover, the photodegradation of either single or binary reactants in aqueous solutions satisfactorily followed the pseudo-first-order kinetics.