Organic Pollutants in the Environment: Remediation, Sampling and Analytical Approaches

November 14, 2003 - 12:00pm
Bldg. 90
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This seminar describes the application of basic environmental chemistry principles to the development of advanced oxidation technologies for water treatment and to the improvement of sampling methods for atmospheric trace organic pollutants. Two different studies illustrate each of these topics.  The first study involves the optimization of novel sonochemical techniques that remove organic pollutants from water. The interaction of gas bubbles with ultrasonic acoustic waves in a liquid can generate transient extreme conditions of temperature and pressure. Those microscopic "hot spots" become active reaction sites for volatile organic solutes and produce radical species (OH, HO2) and oxidants (H2O2) through the sonolysis of water. We investigated the bleaching kinetics of azo dyes and their mechanism of degradation under steady-state ultrasonic irradiation at 500 kHz in a bench-scale reactor. Addition of optimal concentrations of Fe(II) produced a significant increase in the bleaching rate via Fenton's reaction. The combination of ultrasonic irradiation with the addition of ozone exhibited a synergistic effect on the overall mineralization of azo dyes.  Sampling and analysis of trace airborne oxygenated chemicals is challenging due to their chemical lability and poor chromatographic resolution. We evaluated the advantages and limitations of a method based on in-situ derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and subsequent derivatization employing bis(trimethylsilyl)trifluoroacetamide (BSTFA) in concert with gas chromatography/ion trap mass spectrometry (GC/ITMS) for the analysis of ambient air samples collected at the San Francisco Bay Bridge Toll Plaza during rush-hour periods.

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