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Volume 13, No. 2, April 2013, Pages 618-626 PDF(393 KB)  
doi: 10.4209/aaqr.2012.07.0195   

Removal of Ethylene and Secondary Organic Aerosols Using UV-C254 + 185 nm with TiO2 Catalyst

Ken-Lin Chang1, Kazuhiko Sekiguchi2,3, Qingyue Wang2,3, Feng Zhao1

1 Key Laboratory of Urban Environment and Health, Institute of Urban and Environment, Chinese Academy of Sciences, Xiamen 361021, China
2 Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan
3 Institute for Environmental Science and Technology, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan




In this investigation we evaluated the feasibility and effectiveness of ozone-producing UV (254 + 185 nm) irradiation and a TiO2 photocatalyst for degradation of ethylene, which is strongly hydrophobic and does not decompose easily in a humid environment. Tests were performed in a photoreactor (V = 0.55 L) under UV irradiation at various wavelengths (365, 254 and 254 + 185 nm), relative humidities (RH < 1% and RH > 86%), atmospheres (pure N2 and air), residence times (11–33 sec), initial ethylene concentrations in the range of 25–105 ppmv and TiO2 contact areas (86.4–259 cm2) with presumably ambient pressure and temperature.
    The experimental results demonstrated that the use of TiO2 under 254 + 185 nm UV irradiation significantly enhanced the photodegradation of ethylene compared to the case of UV irradiation alone, due to the synergistic effect of photochemical oxidation in the gas phase and photocatalytic oxidation on the TiO2 surface. Photodegradation induced with 254 + 185 nm UV irradiation was compared with photodegradation induced with UV irradiation at wavelengths of 365 and 254 nm. The highest conversion and mineralization levels were obtained with 254 + 185 nm UV irradiation among the three tested UV sources. Moreover, irradiating with 254 +185 nm light generated secondary organic aerosols (SOA) via gas-to-particle conversion of organic compounds in the air stream. The results indicate that the concentration of generated SOAs decreased in the presence of the TiO2 catalyst, and thus that TiO2 may be used to effectively control the emissions of undesirable SOAs.
    In an application test, for photocatalytic oxidation with 254 + 185 nm UV irradiation, corresponding to a flow rate of 0.5 L/min, and an initial concentration of 34 ppmv, over 90% of the inlet ethylene could be degraded.



Keywords: Ethylene; Photochemical oxidation; Photocatalytic oxidation; Ozone-producing UV lamp; Secondary organic aerosols.



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