Kinetic study on the photo-catalytic degradation of pyridine in TiO2 suspension systems

It has been generally agreed that pyridine can be effectively mineralized in aerated TiO2 slurries using near-UV irradiation. The knowledge on the kinetics of the system possesses both practical and theoretical values. The present study, on the base of Langmuir–Hinshewood mechanism, illustrates a pseudo first-order kinetic model of the degradation with the limiting rate constant of 3.004 mg l−1 min−1 and equilibrium adsorption constant 2.763×10−2 l mg−1, respectively. The degradation efficiency in alkali is a little higher than that in acid with a minimum at about pH=5, which is explained by the formation of acid-pyridine in acidic surrounding together with the amphoteric nature of the TiO2 surface. The promotion of H2O2 on the photo-degradation lies in its supplying proper amount of radical dotOH radicals for the inducement stage before surface redox reactions.