Despite extensive research on hazardous wastewater treatment by heterogeneous photocatalysis using titanium dioxide (TiO₂), 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 TiO₂ descends as a film along the internal wall (IW) of a column with the lamp in the center (LFFSIW)....[ Read more ]

Despite extensive research on hazardous wastewater treatment by heterogeneous photocatalysis using titanium dioxide (TiO₂), 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 TiO₂ 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 TiO₂ (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[subscritpt 2] (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 TiO₂ 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.