Kinetic Model for Simultaneous Adsorption/Photodegradation Process of Alizarin Red S in Water Solution by Nano-TiO2 under Visible Light.

The simultaneous adsorption and visible light photodegradation of Alizarin Red S in water solutions were studied in real time mode by using nano-TiO2, such as Anatase and Aeroxide P-25, supported on polypropylene strips. Kinetic results of the overall process were compared with those obtained from separated steps of adsorption and photodegradation previously studied; kinetic advantages were evidenced with the simultaneous approach. From the study of different dye concentrations, a kinetic model has been proposed which describes the overall process. This model considered two consecutive processes: The adsorption of dye on TiO2 surface and its photodegradation. The obtained results were in good agreement with experimental data and can predict the profiles of free dye, dye adsorbed on TiO2 and photoproduct concentrations during the total process.