Influence of TiO2 optical parameters in a slurry photocatalytic reactor: Kinetic modelling

Abstract A kinetic model, based on a proposed reaction photo-mechanism and explicitly dependent on the volumetric rate of photon absorption (VRPA), has been performed and analyzed for the photocatalytic degradation of phenol in aqueous suspensions. UVA–vis simulated solar radiation and three commercial TiO 2 powder photocatalysts, with identical chemical structure but with different morphology and hydrodynamic particle size (P25 Aeroxide ® , P25/20 VP Aeroperl ® and P90 Aeroxide ® provided by Evonik) have been used. The effect of TiO 2 hydrodynamic particle size on the optical coefficients has revealed that this property is playing an important role on the absorbed radiation evaluation. Radiation profiles inside the photoreactor were determined by solving the radiative transfer equation (RTE), and the corresponding kinetic parameters were obtained. A comparative study of TiO 2 loading effect on calculated quantum efficiency (η) revealed P25 was the most photo-efficient catalyst, whereas P25/20 reached similar efficiencies only when higher TiO 2 concentrations were used. On the contrary, P90 presented the lowest photo-efficiency with lower photodegradation rates despite absorbing more radiation. The obtained kinetic model has been successfully validated by experimental data, being able to reproduce the evolution of phenol photodegradation at a wide range of catalyst concentrations for the three studied TiO 2 . In the experimental conditions of this work, low irradiation power conditions can be considered; after simplification, the model adopted a linear dependence on the volumetric rate of photon absorption; showing good agreement between predicted and experimental values, with root-square-mean errors below 5%.