Decomposition of Volatile Organic Compounds in Air Streams by UV/Photocatalysts Process
| Autor: | Chih-Ming Ma, 馬志明 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 The main objective of this study is to develop a simple, energy-efficient, photoreactor for operating at room temperature. In this study, the photoreactor type included a differential-type optical fiber reactor, annular photoreactor and new optical fiber reactor. Gaseous 2-propanol (isopropanol, IPA), trichloroethylene (TCE) and benzene were chosen as the target compound in this study because IPA, TCE and benzene were common indoor air pollutants. A differential-type continuous flow optical fiber photoreactor that used single optical fiber coated with TiO2 photocatalyst as light delivery support of photocatalyst was investigated for treatment of gaseous volatile organic compounds. The decomposition of gaseous volatile organic compounds by UV/TiO2 process in an optical fiber photoreactor was studied under various UV light intensities, humidities, and reaction time of carrier gas (flow rates). Conversions of gaseous volatile organic compounds were increased with increasing light intensity, reaction time. Furthermore, the decomposition of gaseous volatile organic compounds was strongly influenced by humidity in the airflow, and the optimum performance was achieved under relative humidity of 15-25%. Experimental results indicated that TCE had lower adsorption constant but it was the most degraded constituent. This might be that TCE decomposition could lead to formation of free radicals Cl• which accelerated the reaction. The apparent quantum yields for the differential-type optical fiber photoreactor were observed to be higher than those for the annular photoreactor. In this work, designing and fabrication of a new gas-phase optical fiber photoreactor was introduced and operated under various parameters, such as UV light intensity and initial concentration for the photocatalytic decomposition of acetone. Experimental results indicated that increasing the UV light intensity or decreasing initial concentrations of IPA by UV/TiO2 process would result in improving the decomposition and mineralization efficiencies. The apparent quantum yield of the new optical fiber photoreactor is about 2 times greater than that of the annular reactor. The purposes of this research include the investigation relating to the modification of photocatalyst. Modification of photocatalyst via doping metal on the TiO2 photocatalyst is assessed for possible application. The removal and mineralization of IPA under radiation of various light intensities were studied. For experiments conducted with gaseous IPA under UV light irradiation, the photocatalytic activity of Pt or Ag deposited TiO2 surface was significantly superior to that of TiO2 only ones. The increase of UV light intensity and retention time improved the decomposition of IPA. However, both the apparent quantum yield for IPA decomposition and CO2 production were decreased. A mathematical model combining the continuity equations and Langmuir-Hinshelwood (L-H) kinetics was established to adequately describe the reaction behavior of IPA decomposition in the annular photoreactor with various photocatalysts and gaseous volatile organic compounds decomposition in the differential-type optical fiber photoreactor. The apparent quantum yielded can be modeled and calculated for the decomposition of IPA by photocatalytic oxidation in the annular photoreactor coated with TiO2 and Pt/TiO2. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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