Identifier

etd-06302009-221900

Degree

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Document Type

Dissertation

Abstract

The interactions of fine and ultrafine particles with chemicals play a dominant role in determining the mobility and availability of pollutants in the environment. Fine particles in sediments can sequester chemicals from the water column, and release volatile and semi-volatile organic compounds to the gas phase upon exposure to air. Ultrafine particles which are photoreactive can degrade these vapor-phase contaminants, and may transform the molecules into species which are more toxic or hazardous than the parent. As the widespread, commercial use of ultrafine particles becomes more common, understanding the chemodynamics of these particles and their interactions with chemicals in the environment becomes paramount. Flooding in the city of New Orleans caused by Hurricane Katrina introduced numerous sediment-laden pollutants to the city. Of particular interest are contaminated sediments which were deposited inside homes and buildings. The fine particles in these sediments which sequester metal and organic pollutants serve as a direct exposure source to persons working inside the structures, both in the sediment as well as by releasing volatile and semi-volatile organic chemicals to the vapor phase. Mathematical models are needed which can provide a quantitative description of the processes which mobilize and transport contaminants in enclosed buildings, in order to understand the short- and long-term chemodynamic behavior of sediment pollutants inside flood-damaged structures. Two chemodynamic models are developed to describe this behavior, a thermodynamic-based equilibrium model and an unsteady-state fate and transport model. Both models can be used to ascertain the classes and quantities of pollutants to which persons working inside the flooded homes may be exposed. Volatile and semi-volatile organic pollutants in the vapor phase can encounter photoreactive ultrafine titanium dioxide particles, embedded into paint and sunscreen-coated surfaces or as aerosolized particulates. Kinetic data for the degradation rates of organic compounds on these paint and sunscreen surfaces is severely lacking, especially for the semi-volatiles. Surface reaction experiments are carried out in order to collect some of this much-needed data. Observed reaction rates are found to vary as functions of both material thickness, due to mass transfer resistances, as well as ambient relative humidity, through the production of surface hydroxyl radicals.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kalliat T. Valsaraj

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