Jo WK

Vol. 18,  No. 4, pp. 419-425, Dec.  2012

N-doped S-doped Air flow rate Acetone generation Light-emitting-diode

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This work explored the characteristics and the photocatalytic activities of S element-doped TiO2 (S-TiO2) and N element-doped TiO2 (N-TiO2) for the decomposition of gas-phase isopropyl alcohol (IPA) at sub-ppm concentrations, using a plug-flow reactor irradiated by 8-W daylight lamp or visible light-emitting-diodes (LEDs). In addition, the generation yield of acetone during photocatalytic processes for IPA at sub-ppm levels was examined. The surface characteristics of prepared S- and N-TiO2 photocatalysts were analyzed to indicate that they could be effectively activated by visible-light irradiation. Regarding both types of photocatalysts, the cleaning efficiency of IPA increased as the air flow rate (AFR) was decreased. The average cleaning efficiency determined via the S-TiO2 system for the AFR of 2.0 L min^(-1) was 39%, whereas it was close to 100% for the AFR of 0.1 L min^(-1). Regarding the N-TiO2 system, the average cleaning efficiency for the AFR of 2.0 L min^(-1) was above 90%, whereas it was still close to 100% for the AFR of 0.1 L min^(-1). In contrast to the cleaning efficiencies of IPA, both types of photocatalysts revealed a decreasing trend in the generation yields of acetone with decreasing the AFR. Consequently, the N-TiO2 system was preferred for cleaning of sub-ppm IPA to S-TiO2 system and should be operated under low AFR conditions to minimize the acetone generation. In addition, 8-W daylight lamp exhibited higher cleaning efficiency of IPA than for visible LEDs.