Prediction of primary intermediates and the photodegradation kinetics of 3-aminophenol in aqueous TiO2 suspensions

The kinetics of the photocatalytic degradation of 3-aminophenol (3-AP) has been investigated experimentally and theoretically. The reactions have been carried out in a batch-type photoreactor using TiO2 P25 Degussa as the pho tocatalyst. The effects of the catalyst loading, the initial concentration of 3-AP and the electron accepters; H2O2, K2S2O8 and KBrO3 on the degradati on rate have been determined. With the intention of predicting the primary intermediates, geometry optimizations of the reactants, products and the tr ansition state complexes have been performed with the semi-empirical PM3 me thod. The molecular orbital calculations have been carried out by an SCF me thod using RHF or UHF formalisms. Based on the results of the quantum mecha nical calculations, the rate constants of the four possible reaction paths have been calculated by means of the Transition State Theory and 1,4-dihydr oxy-3-amino-cyclohexa-2,5-dienyl radical has been determined as the most pr obable primary intermediate. (C) 2001 Elsevier Science B.V. All rights rese rved.