Author : Chun-Wai Ringo Lam
Publisher : Open Dissertation Press
Page : pages
File Size : 31,20 MB
Release : 2017-01-27
Category :
ISBN : 9781361480571
Book Description
This dissertation, "Development of Photocatalytic Oxidation Technology for Purification of Air and Water" by Chun-wai, Ringo, Lam, 林俊偉, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled "Development of photocatalytic oxidation technology for purification of air and water" Submitted by Lam Chun Wai, Ringo for the degree of Master of Philosophy at the University of Hong Kong in January 2007 The adverse health effect of indoor air pollutants has aroused the attention of scientists and medical personnel since the outbreak of Legionnaires' disease in Philadelphia in 1976. Since then, numerous investigations of indoor air quality have demonstrated the positive correlation between the health risks and exposure to air pollutants such as oxides of nitrogen (NO ), sulphur dioxide (SO ), carbon monoxide x 2 (CO) and volatile organic compounds (VOC). Employees exposed to such pollutants complain of problems such as headaches and irritated eyes. These symptoms are related to elevated indoor air pollutant concentrations, which produce the condition known as sick building syndrome (SBS). There are various types of air purification systems available on the market to reduce the concentration of indoor air pollutants, such as particulate matters, VOC and micro-organisms. High-efficiency particulate air (HEPA) filters, ultraviolet germicidal irradiation (UVGI) lamps and ozone generators are commonly used. However, none of these systems offers a complete solution and some of them may even cause health hazards themselves. The photocatalytic oxidation technology employs a more robust air purification mechanism. When UVA light is incident on photocatalysts, hydroxyl and hydroperoxyl radicals will be generated. These strong oxidizing radicals can decompose VOCs into harmless simple compounds, eliminate odors and destroy microbial bioaerosols. Since the radicals generated stay on the surface of the photocatalyst and no reactive chemical is released into the air stream, the photocatalytic air purification device causes no harm to the building's occupants. This study aims to investigate the use of photocatalysis for indoor air purification. The TiO thin film was characterized with different characterization methods such as 2 Differential Scanning Calorimetry and Thermal Gravity (DSC/TG) analysis, X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), UV- Vis NIR absorption spectra, Scanning Electron microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Common indoor air pollutants such as formaldehyde (HCHO), nitrogen monoxide (NO), nitrogen dioxide (NO ) and airborne bacteria were selected as target compounds. Parametric analyses were conducted with the aforementioned pollutants under different parameters in the presence of TiO . The photodegradation rate, in general, increased with decreasing initial pollutant concentration and increasing UVA light intensity. Airborne bacteria, staphylococcus aureus and mycobacterium tuberculosis (MTB), were successfully photo-degraded by UVA light with the presence of sol-gel TiO . Another objective of this study was to extend the useful spectral range of photocatalyst from UVA light to visible light. It could be done by implantation of chromium (Cr) ion into TiO photocatalyst. The experimental results revealed the effectiveness of the visible-light-assisted Cr/TiO photoreactors in degradation of gaseous formaldehyde. It implied that the photoreactors could be effectively applied to achieve solar photocatalysis.