Degradation of Chlorinated Hydrocarbons via a Light-Emitting Diode Derived Photocatalyst

Abstract

In this study, the applicability of visible light-emitting-diodes (LEDs) to the photocatalytic degradation of indoor-level trichloroethyl- ene (TCE) and perchloroethylene (PCE) over N-doped TiO2 (N-TiO2) was examined under a range of operational conditions. The N-TiO2 photocatalyst was calcined at 650 o C (labeled N-650) showed the lowest degradation efficiencies for TCE and PCE, while the N-TiO 2 pho- tocatalysts calcined at 350oC, 450oC, and 550oC (labeled as N-350, N-450, and N-550, respectively) exhibited similar or slightly different degradation efficiencies to those of TCE and PCE. These results were supported by the X-ray diffraction patterns of N-350, N-450, N-550, and N-650. The respective average degradation efficiencies for TCE and PCE were 96% and 77% for the 8-W lamp/N-TiO2 system, 32% and 20% for the violet LED/N-TiO2 system, and ~0% and 4% for the blue LED/N-TiO2 system. However, the normalized photocatalytic degradation efficiencies for TCE and PCE for the violet LED-irradiated N-TiO 2 system were higher than those from the 8-W fluorescent daylight lamp-irradiated N-TiO2 system. Although the difference was not substantial, the degradation efficiencies exhibited a decreas- ing trend with increasing input concentrations. The degradation efficiencies for TCE and PCE decreased with increasing air flow rates. In general, the degradation efficiencies for both target compounds decreased as relative humidity increased. Consequently, it was indi- cated that violet LEDs can be utilized as energy-efficient light sources for the photocatalytic degradation of TCE and PCE, if operational conditions of N-TiO2 photocatalytic system are optimized.