Date of Award
Doctor of Philosophy
E. L. Wehry
Polycyclic aromatic hydrocarbons, known as PAHs, are a class of organic compounds of concern due to their mutagenic and toxic properties. PAHs are prevalent in the earth's atmosphere, either in the gaseous phase or associated with particulate matter, and can undergo photodecomposition in the atmosphere by direct exposure to sunlight, to produce other compounds, which may or may not be more harmful than the parent PAHs.
Coal fly ash is a major type of particulate matter, with which PAHs may be associated in the atmosphere. The ultimate fate of atmospheric particulate matter, due to the health hazards associated with ingestion of respirable size range particles, especially when these particles contain PAHs or their phototr^formation products, is of substantial interest.
Recent work has shown that the presence of other organic compounds adsorbed on particulate matter, as well as the chemical and physical properties of the particulate matter, may play a substantial role in the photochemistry of adsorbed PAHs. The current study is an attempt to determine what effects the presence of coadsorbed stearic acid and 2- undecanone have on the photochemistry of pyrene adsorbed on coal fly ash.
Pyrene adsorbed on coal fly ash, in the presence and absence of stearic acid or 2- undecanone, was illuminated with a xenon lamp to simulate exposure to sunlight. Both pyrene and stearic acid or 2- undecanone were deposited from the vapor phase onto coal fly ash to achieve varying coverages of each on the fly ash in order to investigate the effect of coverage. The importance of order of deposition on the fly ash was also explored, using stearic acid as the coadsorbate. The amount of pyrene prior to and following illumination was quantified after extraction of pyrene in organic solvent by ultraviolet visible absorption spectrophotometry.
Results showed that the presence of both stearic acid and 2- undecanone increased the extent of photodecomposition of pyrene adsorbed on coal fly ash. Varying the coverage of the coadsorbate had little effect on the extent of photodecomposition of pyrene. Changing the order of deposition of pyrene and stearic acid had no apparent effect on the photodegradation of pyrene adsorbed on coal fly ash.
From the results it was concluded that the chemical properties of the coadsorbates, stearic acid and 2- undecanone, may play a role in the increased photodecomposition of pyrene adsorbed on coal fly ash by acting as an electron acceptor for production of the pyrene cation radical intermediate to the formation of photoproducts, or they may subsequently react with the pyrene cation radical intermediate to produce the pyrene photoproducts.
Sauceman, Sabella Bowers, "The effects of stearic acid and 2-undecanone on the photodecomposition of pyrene adsorbrd on coal fly ash. " PhD diss., University of Tennessee, 2000.