Three-phase photocatalysis using suspended titania and titania supported on a reticulated foam monolith for water purification

This paper presents the first results on the performance of a pilot-scale photocatalytic oxidation reactor having a TiO2-coated 15 pores-per-inch (15 PPI) alumina reticulated foam monolith installed in the annular space between a centrally installed I kW UV lamp and the internal wall of the reactor. Photocatalytic oxidation of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in water was chosen as a test reaction to evaluate the performance of the new reticulated foam photocatalytic reactor and to compare its photocatalytic efficiency with that of the same reactor but with the same mass concentration of TiO2 suspended in water as slurry catalyst. The reticulated foam monoliths were spray-coated with 10 and 12 wt.% Degussa P25 TiO2 (equivalent to 18.58 and 21.78 g/L of water, respectively, in suspension). Results were analyzed in terms of overall DBU conversion, TOC conversion, initial reaction rates per unit reactor volume, photonic efficiency and overall process economics. For the test reaction above, results indicate that the 12 wt.% TiO2-coated reticulated foam photocatalytic reactor was more efficient compared to the reactor using equivalent TiO2 slurry, with DBU conversion of 100%, TOC conversion of approximately 23% and quantum yield of 3.8 (-) achieved in 60 min. The results clearly suggest that immobilised TiO2 could be a cost-effective method that should be taken further to large-scale water purification using heterogeneous photocatalysis. (C) 2007 Elsevier B.V.. All rights reserved.