Date of Award
Level of Access Assigned by Author
Master of Science (MS)
Howard H. Patterson
Second Committee Member
Third Committee Member
Christopher S. Cronan
The environmental fate of pharmaceuticals and personal care products (PPCPs) is a topic of growing interest. Although concentrations of these compounds are very small in the environment, the effects of mixtures of them as well as photooxidation byproducts are not well understood and may pose health risks to humans. Photodegradation of PPCPs is currently a method for decreasing the concentrations of these compounds in the environment, but dissolved organic carbon (DOC) found in natural waters often interferes with photodegradation by binding with these compounds. To better understand this binding and find a way of catalyzing the photodegradation, the binding of several PPCPs with five DOC sources was studied. Silver-doped Y-zeolite was used as a catalyst to enhance photodegradation in the presence of DOC. One ppm solutions of 17α-ethinylestradiol (EE2), bisphenol-A, and ibuprofen were primarily analyzed using synchronous luminescence to monitor a decrease in peak intensity when introduced to solutions of DOC in the dark. These solutions were prepared from the Stillwater River in Orono, Maine, from several Suwannee River standards, and a Leonardite humic acid standard. Synchronous spectra showed peaks of EE2 (310 nm, Δλ = 30 nm), BPA (312 nm, Δλ = 35 nm), and ibuprofen (286 nm, Δλ = 20 nm) decrease in intensity over time after initial mixing with each DOC source in the dark. Solution pH was also varied between pH 3 and pH 10 to observe the influence on binding. Binding constants were determined using Stern-Volmer analysis and were in the order of 104 L/kg for the majority of solutions. Solutions of EE2, BPA, ibuprofen were stirred for one hour under dark conditions and also with exposure to UV light to monitor binding and photodegradation. Additional samples were treated with fulvic acid and fulvic acid with silver-doped Y-zeolite to observe the change in photodegradation rate. Solutions that were not exposed to light showed little change in signal intensity, implying that hydrolysis does not impact degradation. Silver zeolite caused 90% of EE2 to adsorb due to the reactivity of the silver (I) ion. The adsorption of PPCPs was diminished in solutions that also contained DOC due to their binding with DOC with the PPCP’s adsorption. Luminescence intensity of each PPCP signal decreased in both dark and light reactions with all three PPCPs in the presence of DOC, perhaps due to the presence of PPCP-DOC complexes that allowed for higher concentrations of PPCP in solution. After one hour, the decrease in EE2 signal was negligible in the presence of DOC, whereas it decreased to 40% in the presence of DOC and zeolite and to 79% in the presence of DOC, zeolite, and UV exposure. HPLC was used to determine the solution concentrations for each PPCP. These concentrations were used to calculate the degradation rate constants. Both luminescence and HPLC results suggest that using silverdoped zeolite with UV light will increase the rate of photodegradation rate of the studied PPCPs.
Laliberte, William R., "Use of Silver-Doped Zeolite to Enhance the Photodegradation of PPCPs in the Presence of Dissolved Organic Carbon" (2012). Electronic Theses and Dissertations. 1817.