| This study reports the design, the development, the characterization and the utilization of a novel Photo-CREC-Air reactor. This photo catalytic unit operates in a batch mode and features a basket with immobilized TiO 2. The TiO2 is supported on a fiberglass mesh and is illuminated externally by eight Pen-Ray® lamps housed in parabolic reflectors.; Two different configurations for TiO2-mesh placement were considered. Flow patterns for both configurations were studied using CFX-4.3 computational fluid dynamic package. This ensured a good contact between the treated air stream and the photo catalyst.; Two photo catalysts, Degussa P25 and Hombikat UV-100, were employed with the catalytic activity being tested with three representative model pollutants: acetone, isopropanol and acetaldehyde. Reactant, products and intermediates were quantified using a GC equipped with a TCD detector. Carbon dioxide and water were the only products detected in the gas phase during acetone and acetaldehyde photo degradation, whereas acetone was an important gas phase intermediate for iso-propanol photo degradation.; In this study, special emphasis was assigned to the determination of the influence of several operating factors that could affect the reactor efficiency, including catalyst type, catalyst loading, initial reactant concentration, temperature, and light intensity.; Experimental results revealed that the photo conversion rate depends on (a) the physical properties of the photo catalyst, particle-particle agglomeration and particle-mesh interaction, (b) the catalyst loading, (c) the type of the pollutant being treated, (d) the irradiation intensity, and (e) the temperature.; Deactivation experiments demonstrated that catalytic activity decay was a function of the type of the photo catalyst and of the model pollutant. In this study, significant decay was observed in the case of Degussa P25 while used for iso-propanol photo degradation. However, there was no comparable activity decay for Hombikat UV100. No detectable activity decay was observed for Degussa P25 and Hombikat UV-100 during the photo oxidation of acetone and acetaldehyde. Those experiments were also valuable in revealing an increase in the catalyst adsorption capacity with illumination.; Rate equations that describe the photo oxidation rate of acetone, iso-propanol and acetaldehyde were investigated. It was found that the Langmuir-Hinshelwood equation describes the rates of photo degradation, with iso-propanol photo degradation requiring the inclusion of acetone as an intermediate species.; Energy efficiencies were established in terms of the average apparent quantum efficiencies defined as the number of mineralized pollutant molecules at the 90% conversion level per polychromatic photon reaching the catalytic mesh. Values reported ranged between 21–32% for iso-propanol, 28–41% for acetone and 88–157% for acetaldehyde. On the other hand, apparent quantum efficiencies based on the initial reaction rate were 166–423% for iso-propanol, 50–55% for acetone and 345–450% for acetaldehyde. These results indicate the possible role of a chain photo conversion mechanism. |
