LED Irradiation of a Photocatalyst for Benzene, Toluene, Ethyl benzene, and Xylene Decomposition

Abstract

Studies on the use of gas phase applications of light emitting diodes (LEDs) in photocatalysis are scarce although their photocatalytic decomposition kinetics of environmental pollutants are likely different from those in aqueous solutions. The present study evaluated the use of chips of visible light LEDs to irradiate nitrogen doped titania (N-TiO 2 ) prepared by hydrolysis to decompose gaseous benzene, toluene, ethyl benzene, m -xylene, p -xylene, and o -xylene. Photocatalysts calcined at different temperatures were characterized by various analytical instruments. The degradation efficiency of benzene was close to zero for all conditions. For the other compounds, a conventional 8 W daylight lamp/N-TiO 2 unit gave a higher photocatalytic degradation efficiency as compared with that of visible-LED/N-TiO 2 units. However, the ratios of degradation efficiency to electric power consumption were higher for the photocatalytic units that used two types of visible-LED lamps (blue and white LEDs). The highest degradation efficiency was observed with the use of a calcination temperature of 350 °C. The average degradation efficiencies for toluene, ethyl benzene, m -xylene, p -xylene, and o -xylene were 35%, 68%, 94%, and 93%, respectively. The use of blue- and white-LEDs, high light intensity, and low initial concentrations gave high photocatalytic activities for the photocatalytic units using visible-LEDs. The morphological and optical properties of the photocatalysts were correlated to explain the dependence of photocatalytic activity on calcination temperature. The results suggest that visible-LEDs are energy efficient light source for photocatalytic gas phase applications, but the activity depends on the operational conditions. The use of chips of visible light emitting diodes to irradiate an annular reactor coated with a nitrogen doped titania catalyst to decompose gaseous aromatic compounds was studied.