Design, operation and modeling of a falling film photocatalytic reactor

Despite extensive research on hazardous wastewater treatment by heterogeneous photocatalysis using titanium dioxide (TiO{dollar}sb2{dollar}), there are few demonstrations of an effective photocatalytic process on an industrial scale. The purpose of this research was to establish a methodology for the design and modeling of an optimal configuration of photocatalytic reactor irradiated by UV lamps. This configuration was recognized in a laminar falling film slurry (LFFS) photocatalytic reactor in which a slurry suspension of TiO{dollar}sb2{dollar} descends as a film along the internal wall (IW) of a column with the lamp in the center (LFFSIW).; A general design methodology for LFFSIW photocatalytic reactors was developed. On the basis of this methodology, a pilot plant was constructed, commissioned and optimized using commercially available high efficiency UV lamps.; A mathematical model (LSSE-LSPP model) for LFFSIW photocatalytic reactors with five dimensionless parameters was developed. Model solutions were obtained with a minimum number of numerical integrations. As model parameters can be easily estimated from real systems, the model can be therefore used for scale-up. Recommendations for scale-up of the pilot plant are included in this work.; Results obtained under photocatalytic conditions were successfully tested using the LSSE-LSPP model for a wide range of experimental conditions. Sensitivity analysis indicated that kinetic parameters should be determined with a high degree of accuracy. In addition, the model revealed that in the range of 310-380 nm, light scattering in water suspensions of TiO{dollar}sb2{dollar} (Degussa P25), is negligible at high optical thickness but cannot be neglected at low optical thickness. As a consequence, mathematical modeling of the radiation field is necessary for the estimation of the intrinsic kinetic parameters of TiO{dollar}sb2{dollar} (Degussa P25) photocatalyzed reactions.; From the operation of the pilot plant under different experimental conditions, it was found that optimal performance was obtained with an "integrated" method using low pressure mercury lamps irradiating TiO{dollar}sb2{dollar} slurry suspensions containing hydrogen peroxide and oxygen. This "integrated" method yielded one order of magnitude increase with respect to photocatalysis alone, and a two-fold increase with respect to UV-peroxidation alone.