Kinetic modeling for the deactivation of TiO2 during the photocatalytic removal of low concentration SO2

•A deactivation kinetic model for the removal of SO2 with TiO2 is proposed.•The activity of the deactivated catalyst was derived.•The proposed kinetic model is applied to the experimental results under different operation conditions.•Water effects on the reaction and deactivation processes are discussed.

A kinetic model considering the deactivation of a catalyst was developed for the removal of low concentration SO2 with TiO2 as the photocatalyst. For the deactivation caused by poisoning of the reaction products, the catalyst activity which decreased with time was derived based on the Langmuir adsorption assumption. The calculated results of the kinetic model were consistent with the experimental data under various operation conditions, including inlet SO2 concentration, space time, flue gas humidity, and time on stream. The kinetic model can be used to predict the evolution of the outlet SO2 concentration, as well as the catalyst activity, with the operation time and the position of catalyst bed. The influences of water content on the reaction and deactivation processes of the catalyst were discussed based on the obtained kinetic parameters. The reaction and deactivation rate constants both increased with the increase in water content, which means that the presence of water in flue gas will not only promote the photocatalytic reaction of SO2 but also accelerate the deactivation of the TiO2 catalyst.