ABSTRACT
The purpose of this research was to investigate the modified photocatalyst(TiO2) from the heterogeneous photocatalysis of perchloroethylene(PCE) products distribution by different operating conditions using near UV/TiO2 hope that could enhance the PCE¡¦s conversion and mineralization rate and explore the reaction pathways.The modified photocatalyst of this research was completed with Ag/TiO2¡BAu/TiO2¡BPt/TiO2¡BWO3/TiO2 and AC/TiO2. The added species except activied carbon was 10 % weight of photocatalyst(TiO2) others the noble metal (sillver¡Bgold and platinum) and tungsten oxide(WO3) were 0.5 % weight of TiO2. Then the experiments were conducted by varying relative humidity(R.H.=0~60 %), oxygen concentration(0~21 %), and retention time(0.38~0.89 sec).
Glass beds coated with modified Degussa P-25 anatase TiO2 were filled in a Pyrex glass reactor. TiO2 was illuminated by four 10 watts ultraviolet(UV) lamps. Results from QA/QC experiments indicated that PCE could not be photodegradated by near UV of wavelength 365 nm. However, It can be decomposed quickly through heterogeneous photocatalysis. And it also find that no modified photocatalyst would be envenomed in photoactivied continuance test. The best PCE conversion and mineralization rate of modified photocatalyst were WO3/TiO2 and AC/TiO2. The modified photocatalyst Ag/TiO2 were the same as TiO2 but Au/TiO2 and Pt/TiO2 were worse to TiO2. The highest converstion rate of PCE could top to 99.5 %¡F The experiment showed that PCE was decomposed as oxygen concentration and retention time increased. But a higher concentration of oxygen was not efficient on the increase of PCE conversion. The conversion ratio of PCE could be inhibited at higher relative humidities.
The end products observed from UV/TiO2 heterogeneous photocatalytic reactions included CHCl3, CCl4, C2HCl5, C2Cl6, COCl2, CCl3CClO, Cl2, HCl, CO, and CO2. The major chlorinated compound was Cl2 when the photocatalytic reactions proceed at higher oxygen concentration and less humid conditions. As water vapor existed, the major chlorinated compound became HCl. The major product was CO2 during the entire experimental process of heterogeneous photocatalytic reactions.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0731100-155932 |
| Date | 31 July 2000 |
| Creators | Hsiao, Te-Fu |
| Contributors | Yung-she Sae, Chung-Shin Yuan, Ming-Shean Chou, C-H Hung |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0731100-155932 |
| Rights | unrestricted, Copyright information available at source archive |
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