Performance of TiO2 photocatalyst supported on silica beads for purification of wastewater after absorption of reflow exhaust gas

The photocatalytic treatment of wastewater containing organic compounds in the exhaust gas from a reflow furnace is studied in a laboratory-scale batch recirculation type reactor system with a packed column of TiO2/SiO2 beads (TiO2 supported on SiO2 beads). A comparison is made between the photocatalytic activities of the TiO2/SiO2 beads under irradiations with UV light emitted from 6W blacklight blue fluorescent lamps (BL) and germicidal lamps (GL). When the wastewater is treated over 24 h, the conversions on the TOC concentration base are 73 and 90% with UV irradiations from BL and GL, respectively, indicating that CL is more useful for the present photocatalytic treatment. Quantitative and qualitative analyses of the treated wastewater by GC/MS reveal that the photocatalytic reactor system can satisfactorily decompose not only aromatic but also aliphatic compounds into harmless substances (CO2 center dot H2O and other mineral ions). Although several intermediates are present in the treated wastewater, their concentrations are very low. The TiO2/SiO2 photocatalyst can retain more than 80% of the original activity even after repeated use of three times. (C) 2011 Elsevier B.V. All rights reserved.