Kinetics of Photocatalytic Degradation Using Titanium Dioxide Films

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Title: Kinetics of Photocatalytic Degradation Using Titanium Dioxide Films
Author: Chin, Paul
Advisors: Eric A. Stone, Committee Member
Christine S. Grant, Committee Member
H. Henry Lamb, Committee Member
George W. Roberts, Committee Member
David F. Ollis, Committee Chair
Abstract: Titanium dioxide (TiO₂), a semiconductor metal oxide, has been used in heterogeneous photocatalysis for the destruction of organic, inorganic, and biological materials. The chief objectives of my doctoral research are to generate kinetic data and to develop engineering models for photocatalytic oxidation (PCO) using TiO₂ thin films for current challenges in "solid"-solid and air-solid environmental remediation. Three topics are studied in detail: i. TiO₂ Photocatalytic Oxidation for Formaldehyde Removal from Air (Air-Solid) Formaldehyde (CH₂O) is a toxic air contaminant present in industrial, commercial, and residential buildings. A novel rotating honeycomb adsorbent coupled with a PCO reactor was demonstrated by F. Shiraishi and coworkers for CH₂O oxidation. They showed that their cyclic adsorbent ⁄ PCO reactor could oxidize CH₂O to concentrations below the WHO guideline, but they made no attempt to model the system. In this project we modeled their batch system at transient and steady states. In addition, we applied the batch model kinetic parameters to design a continuous system for typical residential home challenges. ii. TiO₂ Photobleaching of Dye Layers as a Field Analysis Method ("Solid"-Solid) Technological advances in the past decade allow glass manufacturers to deposit thin, photoactive, nano-sized TiO₂ layers on glass billed as "self-cleaning" surfaces. Field installation of such "self-cleaning" window glass for office buildings or residential homes will require the creation of field analysis methods to characterize the initial and continuing catalyst activity variations with time and environmental conditions. In this project we characterized the PCO properties of commercial Pilkington Activ™ glass by oxidizing deposited organic dyes (a) to show visual decolorization and recovery of the aesthetic clarity of the glass and (b) to determine the light-driven reaction kinetics on Activ™ glass. iii. TiO₂ Photooxidation of Deposited Soot Layers ("Solid"-Solid) A major contribution to visual degradation of exterior surfaces in urban environments, especially the major cities of industrialized countries, is the deposition of particulate soot. Destruction of deposited soot layers by TiO₂ photocatalysis had been reported recently, but there was (a) an inability to deposit a soot layer of uniform thickness on the TiO₂ surface and (b) a lack of rigorous kinetic modeling. In this project we developed a method to apply a uniform, thin soot layer or a model soot on TiO₂ thin films. We also executed laboratory studies to collect kinetic data for PCO of soot deposits and demonstrated applicability of a series ⁄ parallel reaction network model to describe the kinetics of TiO₂ PCO on these porous carbonaceous layers.
Date: 2008-04-25
Degree: PhD
Discipline: Chemical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/5735


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