Application of Light-emitting-diodes to Annular-type Photocatalytic Reactor for Removal of Indoor-level Benzene and Toluene

Abstract

Unlike water applications, the photocatalytic technique utilizing light-emitting-diodes as an alternative light source to conventional lamp has rarely been applied for low-level indoor air purification. Accordingly, this study investigated the applicability of UV-LED to annular-type photocatalytic reactor for removal of indoor-level benzene and toluene at a low concentration range associated with indoor air quality issues. The characteristics of photocatalyst was determined using an X-ray diffraction meter and a scanning electron microscope. The photocatalyst baked at 350 o C exhibited the highest photocatalytic degradation efficiencies(PDEs) for both benzene and toluene, and the photocatalysts baked at three higher temperatures(450, 550, and 650 o C) did similar PDEs for these compounds. The average PDEs over a 3-h period were 81% for benzene and close to 100% for toluene regarding the photocatalyst baked at 350 o C, whereas they were 61 and 74% for benzene and toluene, respectively, regarding the photocatalyst baked at 650 o C. As the light intensity increased from 2.4 to 3.5 MW cm -1 , the average PDE increased from 36 to 81% and from 44% to close to 100% for benzene and toluene, respectively. In addition, as the flow rate increased from 0.1 to 0.5 L min -1 , the average PDE decreased from 81% to close to zero and from close to 100% to 7% for benzene and toluene, respectively. It was found that the annular-type photocatalytic reactor inner-inserted with UV-LEDs can effectively be applied for the decomposition of low-level benzene and toluene under the operational conditions used in this study.