Marsha Kanan

Date of Award

5-2002

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Advisor

Howard H. Patterson

Second Committee Member

Alice E. Bruce

Third Committee Member

Carl P. Tripp

Abstract

The photodegradation of carbaryl in the presence of Suwannee River natural organic matter (NOM) as well as the presence of AgY zeolites was studied. Two NOM samples were purchased in 2000 and 2001 and labeled as NOM-2000 and NOM-2001, respectively. The synchronous-scan luminescence spectra (SSLS) indicate the presence of different luminophores in the two samples. This suggests that although the compositions of the two NOM samples are similar, isomers composing the NOM mixtures are different. This difference was observed in the effect the two Suwannee River NOM samples had on the photodegradation of carbaryl. In particular, the photodecomposition of carbaryl in the presence of NOM-2001 follows first-order kinetics; whereas, in the presence of NOM-2000 the photodecomposition of carbaryl did not follow first-order kinetics. Moreover, the SSLS of a 3 ppm solution of the NOM-2000 sample shows one band in the high-energy region. This band was quenched and a broad band appeared in the low-energy region as the concentration of the solution increased, indicating that the NOM samples might be forming oligomers at higher concentrations. The polymerized products were also found to affect the photodecomposition rate of carbaryl. Silver-doped Y-type zeolites with different silver loadings were prepared and analyzed spectroscopically. Several emission bands were observed for each AgY sample. Each emission band becomes dominant over the others by selecting the suitable excitation wavelength. Similarly, different SSLS bands were observed and tuned by choosing the reasonable Δλ indicating the presence of several luminophores. Both emission and SSLS indicate the presence of different silver clusters in zeolite Y. The prepared AgY samples were found to catalyze the photodegradation of carbaryl. The study shows that the AgY catalysts were found to increase the photodegradation rate of carbaryl by 3-79 times depending on the amount of silver that was loaded on the Y-type zeolites. The effectiveness of the catalysts was monitored in the presence of Suwannee River NOM. The results indicated that in the presence of 3 ppm NOM and the AgY catalysts, the rate of photodegradation was enhanced, whereas, increasing the concentration of NOM to 15 and 30 ppm decreased the photodecomposition reaction rate. The carbaryl photodegradation products in the absence and presence of the AgY zeolites were quantified using the technique of GC-MS. In the absence of the catalysts, only a-naphthol was produced after a solution of carbaryl was irradiated for up to 12 hours. However, in the presence of the AgY catalysts, a-naphthol and phthalic acid are major photodegradation products that were produced.

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