María L. Satuf

Photocatalytic degradation of an emerging pollutant by TiO2-coated glass rings: a kinetic study

This work presents the photocatalytic degradation of the pharmaceutical drug clofibric acid in a fixed-bed reactor filled with TiO2-coated glass rings. Experiments were carried out under UV radiation. A kinetic model that takes into account radiation absorption by means of the local surface rate of photon absorption (LSRPA) has been developed. The LSRPA was obtained from the results of a radiation model. The Monte Carlo method was employed to solve the radiation model, where the interaction between photons and TiO2-coated rings was considered. Data from experiments carried out with rings with different numbers of catalyst coatings and different irradiation levels were used to estimate the parameters of the kinetic model. A satisfactory agreement was obtained between model simulations and experimental results.

Modeling of a Flat Plate, Slurry Reactor for the Photocatalytic Degradation of 4-Chlorophenol

Heterogeneous photocatalysis employing titanium dioxide has emerged as an efficient method to remove a wide range of toxic compounds from polluted waters. In particular, chlorophenols constitute an important group of aquatic contaminants that have been successfully degraded by photocatalysis. In this work, the modeling of a slurry reactor for the photocatalytic degradation of 4-chlorophenol (4-CP) is presented. The experimental reactor is a thin rectangular parallelepiped limited by two parallel windows made of borosilicate glass. It is illuminated from one side by two tubular UV lamps (UV Philips TLK40/09N) located at the focal axis of cylindrical reflectors of a parabolic cross-section. The flat plate reactor is placed inside the loop of an isothermal, batch recycling system. The model describes the degradation of 4-CP as well as the formation and disappearance of the main intermediate products: 4-chlorocatechol (4-CC) and hydroquinone (HQ). Intrinsic kinetic expressions, previously obtained in a laboratory scale reactor, were employed to solve the mass balance for each species. To take account of the radiation effects on the reaction rate, the radiative transfer equation was solved in the flat plate reactor. The radiation model involves two spatial variables and two angular variables in the direction of radiation propagation.To validate the model, experimental runs were conducted by varying the catalyst loading (0.05, 0.1, 0.5, 1.0 x 10-3 g/cm3) and the 4-CP initial concentration (0.7 and 1.4 x 10-7 mol/cm3). Good agreement was found between simulation results and experimental data. Based on the experimental and predicted concentrations of 4-CP and 4-CC, the root mean square error (RMSE) of the model was 9.9 %.

Reactor modeling in heterogeneous photocatalysis: toxicity and biodegradability assessment

Photocatalysis employing titanium dioxide is a useful method to degrade a wide variety of organic and inorganic pollutants from water and air. However, the application of this advanced oxidation process at industrial scale requires the development of mathematical models to design and scale-up photocatalytic reactors. In the present work, intrinsic kinetic expressions previously obtained in a laboratory reactor are employed to predict the performance of a bench scale reactor of different configuration and operating conditions. 4-Chlorophenol was chosen as the model pollutant. The toxicity and biodegradability of the irradiated mixture in the bench photoreactor was also assessed. Good agreement was found between simulation and experimental data. The root mean square error of the estimations was 9.9%. The photocatalytic process clearly enhances the biodegradability of the reacting mixture, and the initial toxicity of the pollutant was significantly reduced by the treatment.