Name Degree Graduation Year Research Project Title
Paul Chin Ph.D. Summer 2008 Kinetics of Photocatalytic Degradation Using Titanium Dioxide Films

Paul Chin, Ph.D.

Department of Chemical and Biomolecular Engineering
College of Engineering 1 (EB1)
911 Partners Way
Raleigh, NC 27695-7905

Phone: (919) 515-8757
Fax: (919) 515-3465
Rooms EB1 2023 (office) & 2089 (lab)

Email: paul (dot) chin (@) ncsu (dot) edu

Refereed Publications under advisorship of Dr. Ollis:

Oral and Poster Presentations under advisorship of Dr. Ollis: (Speaker Underlined)

PhD Disseration Summary

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, organic indoor air contaminant present in industrial, commercial, and residential buildings. The World Health Organization (WHO) set the permissible CH2O indoor air concentration at a very low level of 0.1 mg/m3. Since the TiO2 PCO kinetics are first order for CH2O concentrations below 10 ppm, pre-concentration of CH2O can increase its destruction rate and improve process performance.

A novel rotating honeycomb adsorbent coupled with a PCO reactor (photoreactor) was demonstrated by F. Shiraishi and coworkers for CH2O oxidation. They showed that their cyclic adsorbent / photoreactor 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 Dried 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 (10-20 nm) on glass, with trademark names such as Pilkington ActivTM, PPG SuncleanTM, and Saint-Gobain BiocleanTM. These products are billed as "self-cleaning" surfaces because they utilize TiO2 photocatalytic oxidation (PCO) and photo-induced superhydrophilicity (PSH) properties. The PCO activity causes progressive oxidation of adsorbed oxidizable molecules and organic particulate matter, while the PSH property allows for water washing removal of partially oxidized molecules and particulates from the TiO2 surface.

Field installation of such "self-cleaning" window glass for office buildings or residential homes will require the creation of field tests to characterize the initial and continuing catalyst activity variations with time and environmental conditions. In this project we continued the recent work by Julson and Ollis on PCO of a sub-monolayer dry dye layer on optically opaque TiO2 powder to determine its potential as an analysis method to measure the PCO activity of commercial Pilkington ActivTM TiO2-coated transparent (optically dilute) glass.

iii. TiO2 Photooxidation of Deposited Soot Layers ("Solid"-Solid)
A major contribution to visual degradation of exterior surfaces (e.g., buildings and statues) in urban environments, especially the major cities of industrialized countries, is the deposition of particulate soot from diesel automobiles, heavy equipment, forest fires, burning wastes, and other incomplete combustion sources of heavier liquid fuels. Moreover, soot accounts for 5-15% contribution to reduced visibility in the United States.

Therefore, a recent area of TiO2 research has focused on tackling this issue. 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 modeling to describe the PCO kinetics of soot disappearance. We developed a method to apply a uniform, thin soot layer on TiO2 thin films. Laboratory studies were conducted to collect quantitative kinetic data via quartz crystal microbalance monitoring, and a mixed series / parallel kinetic reaction model was developed to describe the kinetics of TiO2 PCO on these porous carbonaceous layers.

Previous Masters Thesis Research Completed At North Carolina State University

Masters Thesis Title under advisorships of Dr. George W. Roberts & Dr. James J. Spivey: Preferential Oxidation of Carbon Monoxide on Structured Supports

Refereed Publications under advisorships of Dr. Roberts & Dr. Spivey:

Oral and Poster Presentations under advisorships of Dr. Roberts & Dr. Spivey: (Speaker Underlined)